DG535
Contents
1. The rms jitterm as a function of time delay is shown in Figure 5 for a Tektronix 2465 oscilloscope the DG535 using an internal timebase and for a DG535 with an ideal external source The jitter for time delays longer than 10 seconds using the ideal external source is due to the drift of the analog jitter compensation circuits in the DG535 It can be seen from this figure that the Tek 2465 scope would show an apparent jitter of 1 ns rms at 100 us even though the DG535 s jitter is only 50 ps rms CHANNEL to CHANNEL INTERACTION There is a small interaction pulling between channels A and B and between channels C and D when these channels are set within 10 ns of each ips Tektronix DG535 2465 usingint 100ns Oscilloscope timebase 10ns ins RMS Jitter 100ps 10ps 1ps 10ns 100ns 1us 10us 100us using ideal ext source 10ms 100ms 1s 10s 100s 1000s Delay Setting Figure 5 RMS Jitter other The pulling of one channel by the other is typically less than 100 ps TIME DELAY vs REPETITION RATE The time delay for any channel may change by 200 ps as the pulse repetition rate is changed from single shot to the maximum rate of 1 1 us longest delay The burst mode of triggering is effectively a rapid change of the pulse repetition rate GPIB PROGRAMMING DETAILED COMMAND LIST In all of the commands listed here i j and k are integer values and f t and v2. wide range 0 to 1000 s and low jitter 50 ps rms recommend the DGS535 as the solution to many difficult timing problems in science and industry FRONT PANEL OPERATION SUMMARY POWER BUTTON The unit is turned on by depressing the POWER button All instrument settings are stored in nonvolatile RAM and so the settings are not affected by turning the power on and off The model firmware version and serial numbers for the unit will be displayed briefly when the power is first applied LIQUID CRYSTAL DISPLAY The 20 character LCD is the user interface for all front panel programming operations The wide viewing angle LCD is backlit by an electroluminescent panel for convenient operation in low light level conditions When the keypad is in the cursor mode the contrast of the LCD may be adjusted for optimum viewing by the two right most keys on the front panel MENU KEYS Six Menu Keys select the function to be programmed Most menu items are self explanatory TRIG defines the trigger source DELAY is used to adjust the four digital delays OUTPUT sets the output pulse levels GPIB allows the user to see data received via the GPIB and to set the GPIB address STORE and RECALL provide a convenient method to save all of the instrument settings Detailed descriptions of each of these menus will be given DATA ENTRY KEYS Sixteen keys are used to enter and modify data There are three modes of operation for this keypad th
3. 30 Page 31 Page 39 Page 40 Page 41 Page 41 Page 42 Page 44 SAFETY AND PREPARATION FOR USE This instrument may be damaged if it is operated with the LINE VOLTAGE SELECTOR set for the wrong ac line voltage or if the wrong fuse is installed LINE VOLTAGE SELECTION The DG535 operates from a 100V 120V 220V or 240V 50 or 60 Hz ac power source Before applying a power source verify that the line voltage selector card located in the rear panel power entry module is in the correct position The selected voltage may be seen through the clear window by viewing the power entry module from below To change the line voltage selection remove the line cord slide the window to the right and pull the fuse pull lever out Verify that the correct fuse is installed for the ac line voltage 1 Amp for 100 or 120V and 1 2 Amp for 220 or 240V Pull out the line voltage selector card with a pair of needle nose pliers and insert it with the correct line voltage facing the bottom of the instrument and towards the line cord Verify that the correct line voltage can be seen through the slot that is just above thefuse holder Push the fuse holder back in and install the correct fuse Slide the window to the left and replace the line cord LINE CORD The DG535 uses a three wire power cord for connection to the power source and to a protective ground The exposed metal parts of the instrument are connected to the outlet g
4. GPIB The GPIB address is not affected but the terminator is returned to its default value of a carriage return and a line feed with an EOI GT i JI 1K Specify one to three ASCII codes which will terminate each response from the DG535 The default terminator for any response from the DG535 is a carriage return and a line feed The line feed is accompanied by an EOI Example to change the terminator to line feed only the command would be GT 10 the ASCII code for line feed is 10 decimal The EOI is always sent with the last character of the terminator sequence STATUS COMMANDS ES Returns the Error Status byte The error status byte definition is given below Example if a command was sent to the DG535 with too many parameters bit 1 would be set If the ES command is used to read the error status and no other errors had occurred the value 2 would be returned All bits in the Error Status byte are latched and so will remain set until the ES command is executed All bits are reset to zero after the ES command is executed ESi Returns bit i of the Error Status Byte Example the command ES 5 can be used to check for a delay range error If a delay range error had occurred since the last ES or ES 5 commands had been sent then a 1 would be returned otherwise the value 0 would be returned This command also resets the error bit that is being checked ERROR STATUS BYTE DEFINITION Bit Description Alway
5. The Keypad mode cursor or numeric will be the same as it was the last time the menu item was accessed Some menu items only allow one type of keypad mode for example the GPIB address may only be entered in the numeric mode In the cursor mode only the keys with arrows are active The keys with the green arrows are used to modify the displayed value up down or to move the cursor left right The two keys with grey arrows are used to adjust the LCD display contrast In the numeric mode the entire keypad is active Data may be entered as a floating point number or in exponential notation Entered data may be edited by using the BSP backspace key Backspacing past the left edge of the screen will cancel the command The entered data is actually used when the EXC Execute key is pressed Selecting another menu item will have the same affect as pressing the EXC key Error messages will appear on the LCD to indicate improper commands For example an attempt to decrement a delay below zero will generate the error message Delay Range Error The error message may be cleared from the LOD by pressing any key TRIGGER MENU The top line on the trigger menu is Int Ext SS Bur Line The cursor underlines one of the five modes in the list to indicate Internal External Single Shot Burst or Line trigger The left and right cursor keys may be used to change the mode Subsequent menus which are different for each trigg
6. to 4 Volts the minimum step size is 0 1VDC The specified step size must not cause the output level including the programmed offset to exceed 4V or 3V Example the command sequence OM 5 3 OO 5 0 OA 5 4 0 will select the VARiable mode for output C zero its offset see below and set its amplitude to 4 0VDC Note the importance of setting the offset if the offset was set to a level greater than zero the command OA 5 4 0 would generate an error because the programmed offset plus amplitude would exceed the 4VDC maximum OO i v Output Offset of output i is set to v Volts if in the VARiable mode This command is used to set the offset of an output when in the VARiable mode For pulses which have a rising edge output the offset is the voltage between the lowest output level and ground and so a TTL signal has zero offset and 4VDC amplitude while an ECL signal has 1 8VDC offset and a 1VDC amplitude To invert the polarity of the pulse i e for a falling edge output a TTL output is described as a 4VDC offset an a 4VDC amplitude pulse and an inverted ECL pulse is described by a 0 8VDC offset with a 1 0VDC amplitude OP i j Output Polarity of channel i is inverted j 0 or normal j 1 for TTL ECL or NIM outputs This command sets the polarity of logic pulses at the BNC outputs In all cases normal polarity means that the output will provide a rising edge at the specified time Example the command sequence
7. OM 5 2 OP 5 0 will set the C output for an inverted ECL output i e the output goes from 0 8VDC to 1 8VDC when the channel times out 15 TRIGGER COMMANDS TM i Set Trigger Mode to Int Ext SS or Bur i 0 1 2 3 This command selects between Internal External Single Shot or Burst trigger modes Other trigger commands are then used to completely specify the trigger conditions TR will set the internal trigger rate TL and TS set the trigger level and trigger slope for external triggers SS is used to execute a single shot if in the SS mode and BC and BP set the burst count and burst period for the burst mode The TR TL TS BC and BP commands may be executed at any time regardless of the trigger mode Example The command TM 0 selects the internal rate generator as the trigger source TR i f Set Internal Trigger Rate 1 0 or Burst Trigger Rate i 1 to f Hz The frequency may be any value between 0 001 Hz and 1 000MHz The precision is 0 001Hz below 10Hz or 4 digits if above 10Hz Other digits will be truncated The internal rate generator will settle to the programmed value within 2 seconds after the command is executed significant departures from the programmed value may be expected during the 2 second settling period A simple way to disable triggers during this settling time is to select the single shot trigger mode i e TM 2 Example the commands TM 0 TR 0 100 2 will select the internal trigger mode
8. active for example the trigger level for external triggers will be stored even though the instrument may be operating on internal trigger Example the command ST 3 will save all the instrument settings to the third storage location RCi Recall all settings from location i 1 to 9 Default settings may be recalled from location 0 See the CL command for the values of the default settings that are recalled from location 0 Example the command RC 3 will recall all of the instrument settings which were last stored by the ST command to location 3 The display will show the menu item that was active when the ST 3 command was executed It is possible that the memory contents of the stored settings were corrupted between the time they were stored and when they were recalled If this happens the message Recall Error will be displayed on the LCD and bit 6 of the Error Status byte will be set Example The command sequence RC 3 ES 6 would recall location 3 and check bit 6 of the Error Status byte If a 1 is returned by the ES 6 command then the stored values were found to be corrupted and so the instrument setting will not be changed Memory contents may be lost if the Lithium battery is defective or if large line transients occur TROUBLESHOOTING To start make sure that the power entry module on the rear panel is set for ac line voltage in your area and that the correct fuse is installed The programmed voltage may be seen
9. and set the trigger frequency to 100 2Hz TL v Set External Trigger Level to v Volts This command sets the threshold voltage for external triggers To completely specify the external trigger the TS trigger slope command must also be used Example TM 1 TL 1 00 TS 1 specify the external trigger mode with the trigger level at 1 00VDC with a positive slope These values would be appropriate for triggering on the rising edge of a TTL logic pulse Also see the TZ 0 j command which sets the input impedance for external triggers TS i Trigger Slope set to falling G 0 or Rising Edge i 1 This command selects the slope condition for external triggers It is used with the TM TL and TZ commands to specify the conditions for an external trigger Example the command TM 1 TL 1 2 TS 1 TZ 0 0 specify the external trigger mode a trigger level of 1 2VDC a positive trigger slope and a trigger input impedance of 50Q to ground These trigger conditions would be appropriate for triggering on the rising edge of an ECL logic pulse if it is able to drive a 50Q load to ground TZ 0 j Set the input impedance of the external trigger input to 50Q j 0 or high impedance j 1 Example the command TZ 0 1 will set the input impedance to 1 MQ the command TZ 0 0 will set the input impedance to 50Q SS Single Shot trigger if Trigger Mode 2 Each time this command is issued a new delay cycle will be initiated if on
10. bit is set if too many or too few parameters are sent with a command Bit 0 This bit is set if the command is completely unrecognized IS Returns the Instrument Status byte The definition of the instrument status byte is given below Example if the trigger rate to the DG535 is too high bit 4 of the instrument status byte will be set Sending the command IS will return the value 16 if no other bits have been set All of the bits in the instrument status byte except for the BUSY bit are latched ie if a trigger rate error is detected at any time that bit will stay set until the IS command is sent All bits except the BUSY bit will be reset to 0 after the IS command is executed See the IS i 11 command to test one bit of the Instrument Status byte ISi Returns bit i of the Instrument Status Byte Example the command IS 4 will test bit 4 the trigger rate too high bit The value 1 will be returned if a trigger rate error occurred since the last time the IS or IS 4 command was sent If no error had occurred then the value 0 will be returned INSTRUMENT STATUS BYTE DEFINITION Bit Description Trigger has occurred Busy with timing cycle Command error detected 7 Memory contents corrupted 6 Service request 5 Always zero 4 Trigger rate too high 3 80MHz PLL is unlocked 2 1 0 Bit 7 This bit is set if the instrument settings were corrupted since the last time power was removed The
11. or ECL is selected then no further submenus are needed to specify the outputs both the Normal and Inverted logic levels are available at separate front panel BNC s If VAR is selected then the next two submenus are used to set the amplitude and offset of the outputs 100ps 10us 1ps 100ns 10ns ins Typical Time Error Between Outputs 100ps 10ns 100ns 1us 10us 100us 1ms GPIB MENUS There are three menus which are accessed by the GPIB key They are Data GPIB Address 15 Service RQST EXC The first menu displays the last 15 characters of data that have been received over the GPIB 256 characters are retained in memory and may be viewed by scrolling the display window with the cursor keys Spaces and control codes will not be displayed however special characters for carriage returns and line feeds will be displayed This feature is very useful when debugging computer programs that control the DG535 The GPIB address may be set in the second menu The keypad is automatically placed in the numeric mode for this menu item Any address from 1 to 30 may be entered the default address for this instrument is 15 The third menu allows the user to generate a service request by pressing the EXC button lower right on the front panel A service request is used to attract the attention of the GPIB controller standard 10ms 100ms 100s 1000s Time Between Outputs Figure 3 Maximum Error vs Time
12. processor computes a checksum of RAM contents which contain the instrument settings when a power supply dropout is detected The checksum is again computed on power up If the checksums do not match then the default settings are used see CL command for default settings and the message Memory Failure is displayed A defective Lithium battery or very noisy ac line voltages may cause Memory Failures to occur Bit 6 This bit is set if the unit is currently requesting service of the GPIB controller A service request may be generated by a variety of conditions as specified by the service request mask This bit allows the controller to see if this instrument was the one that asserted the service request line on the GPIB Bit 4 This bit is set if the trigger rate is too fast The instrument requires one microsecond after the last delay has finished to reset all the delay channels If a trigger comes during this time then the front panel RATE LED will be turned on and bit 4 will be set Bit 3 This bit is set if a gross error is detected in the 80MHz PLL This can happen if the rear panel switch is set to EXT reference and the applied 10 0MHz reference is too small or more than a SM i fewpercent off the nominal 10 0MHz If this Set Status Mask for service request to i The service occurs the LCD will display the message Ext request status mask is used to specify which Clk Error Instrument Status bits will generate a GPIB servic
13. the commands DT 2 3 1 5 DT 3 2 2 5 attempt to reference A to B and B to A so that neither is referenced to TO This command sequence would generate a Delay Linkage Error An efficient method to change a delay is to position the cursor under a digit using the SC command and then increment decrement the digit using the IC command OUTPUT CONTROL TZ if i Set the Termination Impedance Output i is configured to drive a 50Q load j 0 or a high Z load j 1 If i 0 this command is used to set the impedance of the external trigger input see the Trigger control section Example TZ 4 1 will configure both the AB and AB outputs to drive high impedance loads The command TZ 4 will then return the response 1 indicating that the AB and AB outputs are configured to drive high impedance loads OM if j Set Output i to Mode j where j 0 3 for TTL NIM ECL or VARiable This command sets the logic level of the front panel outputs If TTL NIM or ECL is selected the polarity of the logic output is specified by the OP command If the VARiable output mode is selected then the output amplitude and offsets may be set with the OA and OO commands Example the command OM 6 0 selects TTL levels 0 to 4VDC for the D output OA i v Amplitude of output i is set to v Volts if in the VARiable mode This command is used to set the amplitude i e the size of the step at an output BNC The maximum step size is limited
14. through a window when the power entry module is viewed from the bottom of the unit Verify that the line cord is plugged all the way into the power entry module and that the power button on the front panel is pressed in When the ac power is applied you should be able to hear the fan the unit will not function properly if the fan is not operating or if the side or bottom vent holes are blocked Set the rear panel switch down to select the INT timebase If this switch is up and a reference is not applied then the error message Ext Clk Error will appear on the LCD LCD CONTRAST If there are no characters on the LCD or the contrast is very poor adjust the contrast with the two right most keys the ones with the gray up down arrows The up arrow will increase the contrast the down arrow will decrease the contrast when the keypad is in the cursor mode COLD BOOT If the instrument turns on but is completely unresponsive to the keyboard then the RAM contents may have been corrupted causing the instrument to hang To remedy this situation turn the unit off then hold down the BSP backspace key down and turn the unit back on again This procedure initializes the RAM User calibration parameters will be overwritten by the factory calibration parameters and GPIB address will be set to 15 QUICK TEST Unplug all cables from the unit and recall the default settings by pressing the RECALL menu key the 0 key
15. used to calibrate the amplitude of the front panel output drivers You will adjust calibration values to get a 0 800 VDC pulse into a high impedance load on the TO A B C D AB and the CD outputs Recall default settings RECALL 0 EXC Use the TRIG Menu key to select Int trigger Press TRIG again to set the rate to 100 KHz Use the DELAY Menu key to set the delays for channel B and channel D to 5 us 20 A B AB C D and CD outputs For each of the outputs TO A B AB C D and CD Connect the output to the oscilloscope input 1 MQ input 200 mV div sensitivity Hold down the BSP key and press the GPIB key to access the amplitude calibration factor for the corresponding channel Use the Up Down cursor keys to adjust the amplitude of the output to 0 800 VDC Output Offset Calibration This procedure is used to calibrate the offset of the front panel output drivers You will adjust calibration values to get zero offset into a high impedance load on the TO A B AB AB C D CD and the CD outputs Recall default settings RECALL 0 EXC Use the TRIG Menu key to select Int trigger Press TRIG again to set the rate to 100 KHz Use the DELAY Menu key to set the delays for channel B and channel D to 5 us Use the OUTPUT Menu key to set all the outputs for High Z loads NIM logic levels between 0 and 0 8 VDC Do this for TO A B AB C D and CD outputs For each of the outputs TO A B AB AB C D
16. used to minimize jitter adjust the full scale analog delays to 12 50ns adjust the offsets and amplitudes of the output drivers adjust the trigger threshold offset and to set the optional TCXO time base to exactly 10MHz Any part or all of the calibration procedure may be done If only an adjustment of the timebase is desired there is no need to do the entire calibration procedure If your calibration attempt only makes things worse you have the option of recalling the factory calibration constants to restore the RAM values to their factory settings REQUIRED EQUIPMENT A 300MHz scope with 500ps div timescale such as a Tektronix 2465 A frequency counter with a timebase better than 0 1ppm such as an HP 5384A with option 004 ovenize timebase to calibrate the optional 1ppm TCXO A pulse generator to provide adjustable amplitude fast risetime less than 5ns pulses such as an SRS DG535 You will also need several 50Q coax cables and about ten 50Q terminators CALIBRATION PROCEDURE Start by setting the instrument to the default settings with a RECALL 0 EXC This will set the trigger mode to Single shot the delays to zero the output levels to TTL normal polarity and configure the output drivers for high impedance loads You should recall the factory calibration values If you are going to do only a partial calibration you may wish to write down calibration values that have been recently entered so that they may reentered wi
17. will cause the output to have half the expected amplitude or to misbehave entirely The cursor left right keys are used in the second submenu to select either standard logic levels for the output or continuously variable offsets and amplitudes If either the TTL NIM or ECL logic levels are selected the next submenu is used to specify the polarity of the output pulse the Normal polarity will provide a rising edge at the output at the set time Inverted polarity will provide a falling edge If VAR variable is selected in the second submenu then subsequent submenus allow the pulse amplitude and offset to be set Both numbers may be entered as floating point numbers or may be modified by the cursor keys The minimum amplitude is 100 mV the maximum amplitude is 4 00 VDC and outputs outside the range of 3 to 4 VDC are not allowed AB and CD OUTPUTS The menus for the AB and CD outputs are similar to the other outputs Example menus for the AB output are shown on the following page AB amp AB Loads High Z AB TTL NIM ECL VAR AB Amplitude 1 00V if VARiable is selected AB Offset 0 50V if VARiable is selected The cursor up down keys select the load impedance for both the AB and AB outputs It is very important that if a 50Q load is specified that a 50Q load be present on BOTH the AB and the AB output BNC s The cursor left right keys select the logic levels for the AB and AB outputs If TTL NIM
18. 8 Standard GPIB SH1 AH1 T6 TEO L4 LEO SR1 RL1 PPO DC1 DT1 CO and El 256 characters are remembered in the command buffer All instrument functions and settings may be controlled over the interface bus 14 x 8 5 x 4 75 Weight 10 lbs Power 70 Watts from 100 120 220 or 240 Vac Warranty One year parts and labor on materials and workmanship vii ABRIDGED COMMAND LIST INITIALIZATION CL Clear instrument GT i j k Specify one to three ASCII codes which will terminate each response from the DG535 STATUS ES ES i IS ISi SM i DISPLAY DL i j k CS i SC i MCi ICi DS string DS DELAYS DT i j t OUTPUTS TZi j OM ifj OA i v OO if v OP if j TRIGGER TM i TR i f TZ 0 j TL v Returns the Error Status byte Returns bit i of the Error Status Byte Returns the Instrument Status byte Returns bit i of the Instrument Status Byte Set Status Mask for service request to 1 Select Display Line to menu i submenu j line k Set Cursor Mode G 0 or Number mode i 1 Move cursor to column i 0 to 19 Move cursor left i 0 or right i 1 Increment i 1 or decrement i 0 the digit at the current cursor location Display a string of 1 20 characters Do not use spaces use_underline_instead or semicolons Clear Display String Delay Time of channel i is set to t seconds relative to channel j Example DT 3 2 1 2E 6 will set B A 000 000 001 200 000 seconds S
19. ALIBRATION MENUS To access the calibration menus you must hold down the BSP key then press a menu key Each menu key is used to access a different calibration factor per the following table Menu Key Name TRIG DELAY OUTPUT Output Amplitude Calibration Jitter Cal Delay TO Delay A Delay B Delay C Delay D Amplitude TO Amplitude A Amplitude B Amplitude AB Amplitude C Amplitude D Amplitude CD Trigger Thres Offset TO Offset A Offset B Offset AB Offset AB Offset C Offset D Offset CD Offset CD Freq Cal Rcl Fact Cal Function Minimize jitter from Ext Trig to A Set TO s full scale analog delay Set A s full scale analog delay do not alter this value Set B s full scale analog delay Set C s full scale analog delay Set D s full scale analog delay Adjust TO s amplitude Adjust A s amplitude Adjust B s amplitude Adjust AB s amplitude Adjust C s amplitude Adjust D s amplitude Adjust CD s amplitude Calibrate Ext Trig Input threshold Adjust TO s output offset Adjust A s output offset Adjust B s output offset Adjust AB s output offset Adjust AB s output offset Adjust C s output offset Adjust D s output offset Adjust CD s output offset Adjust CD s output offset Set optional TCXO to 10 000000 MHz Press EXC to recall factory calibration Use the OUTPUT Menu key to set all the outputs for High Z loads NIM logic levels between 0 and 0 8 VDC Do this for TO This procedure is
20. CB Sheet 1 Microprocessor System GPIB and Digital I O Sheet 2 Slow Counter Timers Sheet 3 Trigger Status and Reset Sequence Sheet 4 Rate Generators Sheet 5 Power Supply and Dropout Detection Sheet 6 System Connectors and Polarity Control Bottom PCB Sheet 1 Trigger Circuit and Gated 80 MHz iii 24 24 24 25 25 25 26 26 27 27 27 27 28 28 28 29 29 29 30 32 32 37 37 38 39 40 41 41 42 45 Sheet 2 10 MHz Reference and 80 MHz PLL Sheet 3 Jitter Compensation Sheet 4 ECL Counters and Resync Circuits Sheet 5 TO Analog Delay and Output Driver Sheet 6 A Analog Delay and Output Driver Sheet 7 B Analog Delay and Output Driver Sheet 8 C Analog Delay and Output Driver Sheet 9 D Analog Delay and Output Driver Sheet 10 AB amp CD Gate Output Drivers Sheet 11 Digital to Analog Converter and Multiplexer Sheet 12 Power Regulators Front PCB Optional Outputs PCB Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Table of Figures DG535 Rear Panel DG535 Front Panel Maximum Error vs Time Delay Apparent Peak To Peak Jitter and RMS Jitter RMS Jitter DG535 Block Diagram DG535 Timing Diagram Top PC Layout Bottom PC Layout Figure 10Front PC Layout Figure 11 Optional Outputs PC Layout Figure 12 Fast Transition Time Modules Figure 13 Fast 2 Volt Output Step iv Page 2 Page 3 Page 6 Page 7 Page 8 Page
21. CD and CD Connect the output to the oscilloscope input 1 MQ input 200 mV div sensitivity Hold down the BSP key and press the OUTPUT key to access the Offset calibration value for the corresponding channel Use the Up Down cursor keys to adjust the offset of the output i e the top of the 0 800 V pulse to zero Jitter Calibration This procedure is used to minimize the timing jitter of all the outputs with respect to an external trigger Apply a fast risetime lt 3 ns 2 V pulse with a 10 KHz repetition rate to External Trigger input of the DG535 under test The same pulse should also go to the CH 1 input of the oscilloscope A good way to do this is to use the TO output from another DG535 which has been set to drive a 50 load to TTL levels Place a tee directly on this output with one cable to the DG535 under test and the other cable to the oscilloscope Both cables should be terminated into 50 Q With this arrangement the TO output sees a 25 Q load and so the pulse amplitude will be 2 V 21 The jitter from the External Trigger input to any output TO A B C or D should be less than 50 ps rms On a non intensified fast oscilloscope triggered at 10 KHz a 50 ps rms jitter will appear as about 200 ps peak to peak jitter Careful attention to trigger levels and termination impedances is required to observe this small jitter DGS535 settings Recall default settings with RECALL 0 EXC Select Ext trigge
22. Delay 6 STORE and RECALL MENUS There are ten storage locations from which setup data may be recalled One of these locations number 0 contains default setup data the other nine locations contain setup information that was stored by the user Because the information is stored in nonvolatile RAM it will be available for recall even if the instrument is turned off All of the instrument s settings are stored even those which are not currently active for example the external trigger threshold is saved even though the instrument is operating on internal trigger Operating data is stored by pressing the STORE key one digit 1 9 to specify the storage location and the EXC execute key Mistakes may be edited with the BSP backspace key Instrument settings are recalled from storage by pressing the RECALL key one digit 0 9 and the EXC execute key If the stored data has been corrupted since it was saved the error message Recall Error will be displayed The error message can be removed by pressing any key A defective Lithium battery or very noisy ac line voltages will cause Recall Errors ACCURACY DRIFT AND JITTER Each of the delay channels A B C and D may be programmed to time out from 0 to 1000 seconds with a resolution of 5 ps The factors Apparent Jitter 500ps div Scope Display which detract from this ideal performance are discussed here ACCURACY The error in the time delay betwee
23. GPIB Address 15 Service RQST EXC Store Recall Comment Output Menu Select TO Output Control Menus Only if VAR selected Only if VAR selected For TTL NIM and ECL A Output Control Menus Only if VAR selected Only if VAR selected For TTL NIM and ECL B Output Control Menus Only if VAR selected Only if VAR selected For TTL NIM and ECL AB output control menu C Output Control Menus Only if VAR selected Only if VAR selected For TTL NIM and ECL D Output Control Menus Only if VAR selected Only if VAR selected For TTL NIM and ECL CD output control menu GPIB Menu Store Menu Recall Menu 13 incorrect cursor mode will have no effect the error Will not be reported in the error status byte SC i Move cursor to column i 0 to 19 This command allows the controller to position the cursor under a particular digit usually in a DELAY menu so that the digit may be incremented or decremented by the IC command A request to position the cursor in a non allowed location for example under the decimal point in a time delay menu will result in a value outside of allowed range error setting bit 2 in the Error Status byte MCi Move cursor left i 0 or right i 1 This command allows the cursor to be moved relative to its present position ICi Increment i 1 or decrement i 0 the digit at the current cursor location This command is used to change a displayed par
24. MODEL DG535 Digital Delay Pulse Generator y S RS Stanford Research Systems 1290 D Reamwood Avenue Sunnyvale CA 94089 U S A Phone 408 744 9040 Fax 408 744 9049 Copyright 1994 1997 2000 All Rights Reserved Revision 2 5 11 2000 DG535 DIGITAL DELAY PULSE GENERATOR OPERATION AND SERVICE MANUAL Table of Contents CONDENSED INFORMATION Safety and Preparation for Use v Quick Start Instructions vi DG535 Specifications vii Abridged GPIB Command List viii Error Status Byte Definition ix Instrument Status Byte Definition ix GUIDE TO OPERATION Introduction Front Panel Features Power Button Liquid Crystal Display Menu Keys Data Entry Keys Trigger Status LED s Delay Outputs Pulse Outputs Option 06 Trigger Inhibit Input Den nm mm Rear Panel Features Power Entry Module TEEE 488 Standard Port 10 000 MHz Reference Option 02 35 Volt Rear Panel Outputs Front Panel Programming Trigger Menu Trigger Submenus Trigger Tricks Delay Menus Output Menus AB and CD Outputs GPIB Menus Store and Recall Menus ISSU BB D D D D ACCURACY DRIFT AND JITTER Accuracy Timebase Drift Jitter Channel to Channel Interaction O O0 O0 N Time Delay vs Repetition GPIB PROGRAMMING Detailed Command List Initialization Commands Status Commands Error Status Byte Definition Instrument Status Byte Definition Display Control Commands Delay and Output Commands Delays Output Co
25. ameter in a manner analogous to operating a thumbwheel switch DS string Display a string of 1 to 20 characters This command allows the controller to display a message on the DG535 s liquid crystal display As with all data that is sent to the DG535 spaces will be stripped from the transmitted data so the program should use the underline character to_separate_words Also do not use semicolons as they are reserved characters which allow several characters to be sent on the same line If the DS command is sent without a string then the display will be cleared and the menu item which was displayed before the DS string command was used will be displayed DELAY AND OUTPUT COMMANDS The Delay and Output commands use integer codes which are assigned to each front panel BNC The table for these assignment is given below 14 Integer Assignment 0 Trigger Input 1 TO Output 2 A Output 3 B Output 4 AB and AB Outputs 5 C Output 6 D Output 7 CD and CD Outputs DELAYS DT i j t Delay Time of channel i is set to t seconds relative to channel j Example DT 3 2 1 2E 6 will set B A 0 000 001 200 000 seconds The command DT 2 1 10 5 will set A T0 10 500000000000 seconds Setting delays shorter than 0 or longer than 999 999 999 999 995 seconds will set bit 2 of the Error Status Byte A Delay Linkage Error bit 4 of the Error Status Byte is caused by an attempt to totally disconnect a time reference from TO For example
26. and the EXC key in sequence The trigger menu will appear on the LCD with the cursor under Ss for single shot Press TRIG to select this mode To trigger the unit once press the EXC key The TRIG and BUSY LED s on the left side of the instrument 17 will blink once each time the EXC key is pressed Now press the left arrow key the 4 key twice to select the Internal trigger source The default trigger rate is 10 kHz so the TRIG and BUSY LED s will now glow steadily Trigger an oscilloscope on the rising edge of the TO output and use the scope to look at the output from channel A on the 1us per division scale The default time delays are all zero Press the DELAY Menu Key to show the A delay setting Use the left right cursor keys to position the cursor beneath the lus digit seventh from the right Use the up cursor key to increment the delay in lus increments The rising edge of the A output will move lus later each time the up cursor key is pressed The RATE error LED will come on if the delay setting exceeds 99s as the trigger period is 100us 1O0kHz and lus is required for the reset cycle If channel A is set for a longer delay than any of the other channels its pulse will have a constant pulse width of about 800ns OUTPUT LEVELS If an output has only half of the programmed amplitude then it is very likely that a high impedance load was specified in the OUTPUT Menu but a 50Q load is attached If an output b
27. and there is no cursor mode in the panel interactions STORE and RECALL Menus Selecting an DISPLAY CONTROL COMMAND DL i j k Select Display to show menu i submenu j line k The menu submenu and line number designations are given in the table below DISPLAY LINE SELECT TABLE ijk Display Example Comment Int Ext Ss Bur Line Trigger Mode Menu Rate 1234000 123Hz Internal Trigger Rate Threshold 1 23V External Trigger Menu Slope Trigger Term 50Q Single Shot EXC Single Shot Trigger Rate 1234000 000Hz Burst Trigger Menu Pulses Burst 12345 Periods Burst 12345 A T 123 456789123450 Delay Menus B A 0 123456789125 C B 23 456789123455 D T 0 000000000005 12 Display Example TO A B AB C D CD TO Load 50Q TO TTL NIM ECL VAR TO Amplitude 1 23 TO Offset 2 00 TO Inverted Normal Load 50Q TTL NIM ECL VAR Amplitude 1 23 Offset 2 00 Inverted Normal ae ae se cee Load 50Q TTL NIM ECL VAR Amplitude 1 23 Offset 2 00 Inverted Normal w w w w AB amp AB Loads 509 AB TTL NIM ECL VAR AB Amplitude 1 23 AB Offset 2 43 Load 50Q TTL NIM ECL VAR Amplitude 1 23 Offset 2 00 Inverted Normal Load 50Q TTL NIM ECL VAR Amplitude 1 23 Offset 2 00 Inverted Normal vgy aana CD amp CD Loads 509 CD TTL NIM ECL VAR CD Amplitude 1 23 CD Offset 2 43 Data GPIB Strings
28. ar panel BNC s to provide amplified outputs for TO A B C and D These outputs have nominal adjustable output amplitudes from 32 to 32 Volts The pulse width is approximately 1 us and the leading edge has a transition time of 2 to 3 ns The outputs are designed to drive 50Q loads however if the cable is terminated into a high impedance load the pulse amplitude will double up to 64 Volts for a duration equal to the round trip cable delay The amplitude of the output pulse is reduced by 2 Volts per mA of average output current the average output current is only 0 7 mA for a 32 Volt output into 50Q at a 1 kHz repetition rate For high impedance terminations charging and discharging of the cable capacitance may be the OUTPUT L RECALL Figure 2 DG535 Front Panel E STANFORD RESEARCH SYSTEMS INC MODEL DG535 FOUR CHANNEL DIGITAL DELAY PULSE GENERATOR most important current factor In this case the average current is given by I 2Vtf Z where V is the pulse step size t is the length of the cable in time 5 ns meter for RG 58 f is the pulse repetition rate and Z is the cable s characteristic impedance 50Q for RG 58 FRONT PANEL PROGRAMMING Pressing a new menu key will take you to the top menu for that item Each successive press of the same menu key will take you to the next submenu for that item The power up menu will be the same menu that was displayed when the unit was last turned off
29. e request For example if the command SM 16 is Bit 2 This bit is set whenever a trigger occurs sent then a service request will be generated if the that starts a delay cycle Triggers which occur trigger rate too high bit is set When a service during a delay cycle do not set this bit rather request is generated the corresponding bit in the they will set bit 4 the rate error bit Service Request Mask is turned off This will prevent an uncontrolled stream of service requests Bit 1 This bit is set if the unit is currently busy from being generated by the DG535 To re enable with a timing cycle Unlike all of the other the service request the controller must again set the status bits it is not latched rather it reflects the service request mask with the SM i command current status of the unit and it is not reset when read by the IS command it is reset when CS i the unit finishes the current timing cycle Set Cursor Mode i 0 or Number mode i 1 The unit must be in the cursor mode CS 0 for the SC Bit 0 This bit is set if a command error is MC or IC commands to work Note that certain detected If this bit is set the controller should menu items allow only one type of cursor mode For read the Error Status Byte to determine the exact example there is no numeric mode for the menu nature of the command error Command errors item which selects between TTL NIM ECL and can originate from either the GPIB or from front VAR outputs
30. e is not already in progress provided that the single shot trigger mode has been selected Example the commands TM 2 SS SS SS will place the instrument in the single shot mode and trigger it three times BC i Burst Count of i 2 to 32766 pulses per burst This command is used to specify the number of pulses which will be in each burst of pulses when in the burst mode The Trigger Rate and Burst Period commands are also used to completely specify the burst mode of operation Example the command sequence TM 3 TR 1 1000 BC 4 BP 10 selects the burst mode sets the trigger rate to 1000Hz and specifies 4 pulses per burst Each burst is separated by 10 triggers so that a new burst will start every 10ms BP i Burst Period of i 4 to 32766 triggers per burst This command specifies the number of triggers between the start of each burst of pulses when in the burst mode The burst period must always be 16 at least one larger than the Burst Count Example the command TM 3 TR 1 1E5 BC 100 BP 101 sets the burst mode of operation with a trigger rate of 100KHz There will be 100 pulses in each burst one trigger will be skipped and a new burst of pulses will start STORE and RECALL COMMANDS STi Store all instrument settings to location i 1 to 9 This command allows nine complete setups to be stored in the instrument s nonvolatile RAM All of the instrument s settings are stored even those that are not currently
31. e mode is indicated by the three LED s in the center of the panel The cursor mode lt gt allows individual digits to be modified in a fashion similar to the operation of thumbwheel switches The numeric mode NUM allows the data to be entered as a numeric string The remote mode REM lets the GPIB controller lock out front panel operation The key beneath the Mode LED s allows the user to change the keypad mode if not locked out by the GPIB controller TRIGGER STATUS Five LED s are used to indicate the trigger status The TRIG LED blinks each time the unit is triggered the BUSY LED is on whenever a timing cycle is in progress the RATE LED is lit if a trigger is received while BUSY The INT LED indicates that the internal rate generator is the trigger source and the 50Q LED is on when the EXT TRIG input is terminated in 50Q The EXT TRIG BNC is the input for external triggers DELAY OUTPUTS There are five delay output BNC s TO A B C and D TO marks the start of the timing interval and is most useful when an internal trigger source has been selected The logic transitions at the outputs of A B C and D may be set from 0 to 1000s in 5 ps increments with respect to TO The outputs may be programmed for TTL NIM ECL or adjustable output levels and can drive 50Q or high impedance loads The polarity of each output may be set to provide a rising or a falling edge when the channel times out The outputs will remain asserted un
32. ehaves very erratically then it is very likely that a 50Q load was specified but a high impedance load is attached The pulse outputs AB and CD will misbehave if a 50Q load is specified for these outputs but a 50Q load is attached to only one side of the pair i e to the AB output but not to the AB output JITTER The most common causes of excess jitter are 1 incorrect external trigger threshold setting 2 noise or amplitude fluctuations on the trigger input 3 insufficient or excessive trigger amplitude 4 blocked or stalled cooling fan or 5 triggering at too high a rate The instrument is specified to have a jitter of 50ps 0 01ppm of the delay rms The peak to peak jitter as seen on an oscilloscope is approximately four times the rms jitter hence one would expect to see about 200ps peak to peak on an oscilloscope for short delays GPIB PROBLEMS The first requirement for GPIB operation is to properly attach GPIB cable and to specify the correct address for the instrument The default GPIB address is 15 but any address between 1 and 30 may be set from the front panel To check the GPIB address press the GPIB menu key twice A new GPIB address may be entered by keying in the number and pressing the EXC key The DG535 will respond to commands only if it is addressed and the Remote Enable line REN is asserted When this happens the front panel 18 goes to the REMote state which disables all of the key
33. er mode are selected by pressing the TRIG menu key again TRIGGER SUBMENUS Mode Menu Example Int Rate 10000 000Hz Ext Threshold 1 00V Slope Trigger Term HighZ SS Single Shot Exc Bur Rate 10000 000Hz Pulses Burst 10 Periods Burst 20 Line No submenu The Internal trigger mode has only one submenu to set the trigger rate The rate may be entered in the numeric mode or modified in the cursor mode Only four digits of precision are allowed and digits more than three places beyond the decimal point will be truncated The External trigger mode has three submenus to specify the threshold slope and termination impedance of the external trigger input Each submenu is selected by pressing the TRIG key The Threshold may be entered as a floating point number or may be modified in the cursor mode The Slope may be selected by using the cursor up down keys as can the Trigger termination impedance The threshold slope and termination impedance shown in the example menus would be appropriate for triggering on the rising edge of a TTL Pulse The Single Shot trigger mode has only one submenu If SS is selected by the cursor pressing the TRIG menu key will display Single Shot EXC Now each press of the execute key will trigger the timing cycle The Burst mode has three submenus to specify trigger rate number of pulses per burst and number of periods between the start of each burst of pulses All of the ite
34. et the Termination Impedance Z Output i is configured to drive a 50Q load j 0 or a high Z load j 1 Set Output i to Mode j where j 0 3 for TTL NIM ECL or VARiable Output amplitude of output i is set to v Volts if in the VARiable mode Output Offset of output i is set to v Volts if in the VARiable mode Output Polarity of channel i is inverted j 0 or normal j 1 for TTL ECL or NIM Set Trigger Mode to Int Ext SS or Burst 1 0 1 2 3 Set Int Trigger Rate i 0 or Burst Trigger Rate i 1 to f Hz Set Trigger input impedance to 50Q i 0 or to high impedance j 1 Set External Trigger Level to v Volts Trigger Slope set to falling i 0 or Rising Edge i 1 Single Shot trigger if Trigger Mode 2 Burst Count of i 2 to 32766 pulses per burst Burst period of 1 4 to 32766 triggers per burst STORE and RECALL STi RCi Store all instrument settings to location i 1 to 9 Recall all settings from location i 1 to 9 Default settings may be recalled from location 0 viii ERROR STATUS BYTE Bit Description Always zero Recalled data was corrupt Delay range error Delay linkage error Wrong mode for the command Value is outside allowed range Wrong number of parameters Unrecognized command 7 6 5 4 3 2 1 0 NOTES In all of the commands listed here 1 j and k are integer values and f t and v may be integer floating point or exponential notation Optional parameters are enclosed in curly brackets If opt
35. h the character just to the right of the equal sign and the cursor up down keys are used to select from the available links Not all links are available for example in the above menus linking channel A to channel B is not allowed as B is linked to channel A in the second menu Delay can be scrolled by first selecting the delay menu positioning the cursor under the digit to be incremented Depress the 5 and either the up or down keys simultaneously The step rate will be approximately 4 Hz and may vary during a scan OUTPUT MENUS The output menus are used to specify the load impedances pulse output amplitudes offsets and polarities for each of the front panel BNC s The cursor left right keys are used in the top line of the OUTPUT menu to select which output is to be programmed Successive presses of the OUTPUT key will access each menu line for the selected output finally returning to the top line The menu items for the TO A B C and D output are virtually identical An example of these menus is given here for channel A s output A load High Z A TTL NIM ECL VAR A Inverted Normal if TTL NIM or ECL is selected A Amplitude 1 00V Gf VARiable is selected A Offset 0 50V if VARiable is selected The first line in this submenu specifies the load impedance The cursor up down keys are used to select between High Z and 50Q loads This is a very important step in setting up the output the wrong choice
36. ional parameters are omitted then the current value of those parameters will be sent back to the GPIB controller For example the command TM 3 sets the Trigger Mode to mode 3 while the command TM will return the response 3 Also blanks are ignored case is ignored multiple commands may be sent on one line if separated by semicolons All responses are terminated by a carriage return and a line feed The line feed is sent with an EOL INSTRUMENT STATUS BYTE Bit Description Memory contents corrupted Service request Always zero Trigger rate too high 80MHz PLL is unlocked Trigger has occurred Busy with timing cycle Command error detected O D Gi a The Delay and Output commands use integer codes which are assigned to each front panel BNC The table for these assignment is given below Integer Assignment 0 Trigger Input 1 TO Output 2 A Output 3 B Output 4 AB and AB Outputs 5 C Output 6 D Output 7 CD and CD Outputs GUIDE TO OPERATION INTRODUCTION The DG535 Digital Delay and Pulse Generator can provide four precisely timed logic transitions or two precisely controlled pulses The four digitally controlled time intervals may be programmed from the front panel or via the GPIB Front panel BNC s provide high slew rate outputs at TTL NIM ECL or continuously adjustable levels The outputs may be set to drive either 50Q or high impedance loads The high accuracy 1 ppm precision 5 ps
37. may be integer floating point or exponential notation Optional parameters are enclosed in curly brackets In general if optional parameters are omitted then the current value of those parameters will be sent back to the GPIB controller For example the command TM 3 sets the Trigger Mode to mode 3 while the command TM will return the response 3 Command errors will be reported in the Error Status Byte The controller should verify that the Error Status Byte is zero after each command is sent a nonzero value indicates a programming problem When an error is detected all of the pending commands in the communication buffer are cancelled Also blanks are ignored case is ignored multiple commands may be sent on one line if separated by semicolons All responses are terminated by a carriage return and line feed The line feed is sent with an EOI INITIALIZATION COMMANDS CL Clear instrument The communication buffers are cleared and the default settings are recalled The instrument default settings are Trig Trigger mode set to Single Shot ie triggers are off The default trigger rate is 10 000 Hz Trigger rate 10 000Hz 10 pulses per burst and 20 periods per burst 1VDC positive slope high impedance termination All delays A B C and D are linked to TO and set to Zero All outputs are set to drive high impedance loads to TTL levels Internal Burst Mode External Delays Outputs 10
38. ms may be entered in the numeric mode or modified in the cursor mode The Rate may be entered in floating point or exponential notation and may be specified to four digits of precision For the entries shown in the above menu example there would be 10 pulses per burst each pulse separated by 100 us and a new burst of pulses would start every 20 periods i e every 2 ms The Line trigger mode has no submenus The unit will be triggered on a zero crossing of the power line at the line frequency The line trigger is also synchronized to the internal 80 MHz timebase so that the timing jitter of the delay outputs in this trigger mode will be very low typically 25 ps rms TRIGGER TRICKS There are several techniques that may be used to extend the versatility of the DG535 s trigger modes The Jitter of the delay outputs will be reduced by about a factor of two to less than 25 ps rms if the unit is triggered synchronously with the 10 MHz time base This is done automatically if the Line Trigger is selected You may also want to arrange your external trigger so that it is synchronous with the 10 MHz output on the rear panel if the internal time base is being used It is often desirable to trigger the unit at a sub multiple of the trigger source Suppose you wish to trigger a laser at 10 Hz synchronously with the zero crossing of the power line In this case you would select the Line Trigger and set channel D s delay to 95 ms Once t
39. n any two outputs is less than 1500 ps 500 ps typical Timebase error x Time between Outputs This specification is exclusive of time shifts due to slew rates at the outputs i e it should be measured with both outputs set for the same logic levels driving the same loads The timebase error depends on the timebase being used Standard lt 25 ppm 0 50 C Option 03 lt l ppm 0 50 C External Source spec 0 0002ppm Using the typical error figure for a time delay of 1 0 ms this table implies an absolute error of 25 ns 1 5 ns and 0 5 ns respectively for the standard optional and external timebases assuming a 0 01 ppm external source specification If A 100 000us and B 100 01ps the error with respect to TO will be 2 6 ns with the standard timebase however the accuracy of A with respect to B will be 500 ps A graph showing the maximum time error as a function time delay is shown in Figure 3 The four curves show the time error for the standard optional 0 01 ppm external and ideal external timebases The excess error for time delays longer than 1 second on the ideal external source curve is due to drift in the analog jitter compensation circuits RMS Jitter 50ps Apparent Jitter Gaussian Distribution Figure 4 Apparent Peak To Peak Jitter and RMS Jitter TIMEBASE DRIFT The drift of the timebase over several hours is substantially less x10 to x100 less than the absolute timebase error The majo
40. nd D Range 0 to 999 999 999 999 995 seconds Resolution 5 ps Accuracy 1500 ps timebase error x delay Timebase Standard 25 ppm crystal oscillator Optional 1ppm TCXO Opt 03 External user provides 10 0 MHz reference RMS Jitter Ext Trig to any output 60 ps delay x 10 8 TO to any output 50 ps delay x 10 8 Trig Delay Ext Trig to TO output 85 ns Rate Single shot 001 Hz to 1 000 MHz or Line Resolution 0 001 Hz below 10 Hz otherwise 4 digits Accuracy Same as timebase Jitter 1 10 000 Settling lt 2 seconds for any rate change Burst Mode 2 to 32766 pulses per burst at integer multiples 4 to 32767 of the trigger period External Trigger Rate dc to 1 1 us longest delay Threshold 2 56 Vdc Slope Trigger on rising or falling edge Impedance 1 MQ 40 pF or 50Q Option 06 TTL front panel trigger inhibit input TO A B C D AB AB CD and CD Load 50Q or high impedance Risetime 2 to 3 ns typical Slew Rate 1 Volt ns Overshoot lt 100mV 10 of pulse amplitude Levels TTL 0 to 4 Vdc normal or inverted ECL 1 8 to 8 Vdc normal or inverted NIM _ 8 to 0 Vdc normal or inverted VAR Adjustable offset and amplitude between 3 and 4 Vdc with 4V maximum step size Accuracy 50 mV 3 of pulse amplitude Option 02 Rear panel TO A B C D outputs for lus pulses amplitudes typically x8 of corresponding front outputs at 1kHz rep rate Output level is reduced by 2V mA of additional average output current IEEE48
41. ntrol Trigger Commands Store and Recall Commands TROUBLESHOOTING LCD Contrast Cold Boot Quick Test Output Levels Jitter GPIB Problems CALIBRATION Required Equipment Calibration Procedure Trigger Threshold Calibration Optional 1 ppm Internal Timebase Calibration Output Amplitude Calibration Calibration Menus Output Offset Calibration Jitter Calibration Jitter Cal Factor Delay Cal Factor CIRCUIT DESCRIPTION Microprocessor System TEEE 488 Interface Keypad and LED Indicators LCD Display Output Ports on the Top PCB Output Ports on the Bottom PCB Port Address Decoding Input Ports Digital to Analog Converter Timebase ii 10 10 10 10 11 12 14 14 14 15 16 17 17 17 17 17 18 19 19 19 19 20 20 21 21 21 21 22 22 22 22 22 22 23 23 24 24 Frequency Synthesizer Line Trigger Trigger Selection Trigger Circuits Trigger Sequence Overview of the Delay Channels Jitter Compensation Jitter Precharge and Sample amp Hold Kickpulse The TO Delay Channel A s Digital Delay Analog Delays Reset Cycle and Status Bits Output Drivers Offset Control Impedance Control Gate Output Drivers Power Supplies Rear Panel Output Drivers PARTS LISTS Top PCB Bottom PCB Front PCB Optional Outputs PC Board Miscellaneous and Chassis Assembly PC LAYOUT Top PCB Bottom PCB Front PCB Optional Outputs PCB FAST TRANSITION TIME MODULES SCHEMATIC DIAGRAMS Top P
42. r 1 00 V threshold slope 50 Q Term Set Delay A 100 ns B C D to 1 us Connect the A output to the oscilloscope s CH 2 input Scope settings CH 1 and CH 2 inputs both terminated into 50 Q Trigger on CH 1 with trigger threshold set to 1 00 V 500 mV div sensitivity on both channels Main timebase set for 50 ns div Delayed timebase set for 5 ns div Center CH 2 trace and horizontal expand x10 to 500 ps div Change CH 2 sensitivity to 200 mV div Jitter Cal Factor Hold down the BSP key and press the TRIG key to access the Jitter Cal factor Adjust the Jitter Cal factor to minimize the jitter from the External trigger to the A delay output Delay Cal Factors For each of the channels TO B C and D not A Set the delay for the selected channel to 100 ns all other delays to 1 us Skip this step for TO Connect the selected delay to the CH 2 input of the oscilloscope Hold down the BSP key and press the DELAY key to access the delay factor for the corresponding delay output Adjust the delay factor to minimize the jitter between the External trigger and the delay output
43. r factor in the timebase drift is the instrument s temperature after the instrument has warmed up the timebase drift is about 0 5 ppm C for the standard timebase and about 0 05 ppm C for the optional timebase The drift between several DG535 s which are used in the same experiment may be eliminated by daisychaining the reference output from one DG535 to the reference input on the other DG535 s JITTER Various noise sources in the DG535 modulate the time delay for the outputs causing jitter Some of these noise sources are common to all of the channels others are independent The distribution of the pulses around the desired time can be approximated by a Gaussian or normal distribution oven where p t probability of pulse occurring at time t T set time for the output mean value standard deviation of the distribution Figure 4 shows the shape of the Gaussian distribution and the relations between the rms jitter and the peak to peak jitter The rms jitter is a function of the delay setting The jitter is about 50 ps rms for delays less than100 us For short delays the peak to peak jitter measured on an oscilloscope is about four times the rms jitter For long delays the observed jitter measured on an oscilloscope is primarily due to the jitter of the oscilloscope s horizontal timebase deflection circuits For a good 300 MHz oscilloscope the rms jitter is typically 25 ps 10 ppm of the time base
44. riggered the DG535 will ignore other triggers until all channels have timed out hence every sixth Line trigger at 60 Hz will cause a new timing cycle The RATE error LED on the front panel will be illuminated to indicate that triggers occurred while the unit was busy Trigger rates up to 100 MHz can be used with the unit ignoring all triggers until all channels have timed out as in the above case DELAY MENUS There are four delay menus to specify the delays for channels A B C and D Each delay may be entered in floating point or exponential notation or may be modified in the keypad cursor mode The maximum time delay is 999 999 999 999 995 seconds which may be set with a resolution of 5 ps Example Delay Menus A T0 0 123456789125 B A 0 001000000000 C T0 123 456789123455 D C 0 000000010000 Any delay channel may be linked to another channel Two examples of this are shown in the above sample menus While A is referenced to TO channel B s delay is set to A s delay plus 0 001 seconds Linking provides a convenient method to specify a pulse output AB as a pulse start time and width rather than start and stop times Now if channel A s delay is modified B s delay moves with it so that the pulse width stays at 0 001 seconds With the above settings the CD output will produce a very accurate 10 ns pulse despite the very long delay which is specified for channel C To change the linkage the cursor is positioned beneat
45. round to protect against electrical shock always use an outlet which has a properly connected protective ground To avoid shock or injury do not remove product covers or panels Do not operate the product without all covers and panels in place CONNECTION TO OTHER INSTRUMENTS All front panel BNC shields are connected to the chassis ground and to the power outlet ground via the power cord Do not apply any voltage to either the shields or to the outputs The outputs are not protected against connection to any potential other than ground QUICK START INSTRUCTIONS 1 Make certain that the correct line voltage 1s selected on the rear panel 2 Press the power button in to turn on the unit 3 Press the RECALL Menu key the 0 digit and the EXC key in sequence to recall default settings 4 Press the left cursor key lt twice to select internal trigger 5 Trigger the oscilloscope on the rising edge of TO s output and display A s output on the lus div scale 6 Press the DELAY Menu key and use the cursor keys to change the A delay from 0 0 seconds 7 If you ever change the OUTPUT Menu be sure to specify the correct load impedance 8 If you have problems read the detailed descriptions and troubleshooting sections that follow vi DELAYS INTERNAL RATE GENERATOR INPUTS OUTPUTS COMPUTER INTERFACE GENERAL Dimensions DG535 SPECIFICATIONS Channels Four independent delay outputs B C a
46. s except the keyboard mode key which allows the user to leave the REMote state The program can prevent users from using the keyboard by asserting the Local Lockout state LLO Different GPIB controllers expect different string terminators to finish each response from an instrument The default GPIB terminator for the DGS35 is a carriage return and a linefeed with an EOI The GT command may be used to change the GPIB terminator if your controller requires a different one CALIBRATION There are hundreds of bytes of calibration data in ROM which are determined when the instrument is calibrated at the factory Most of these calibration bytes will never need to be adjusted they correct for unit to unit variations which will not change with aging Other calibration bytes may need to be adjusted to re calibrate the instrument All of the calibration bytes are stored in ROM however those which may need to be adjusted are also stored in nonvolatile RAM The RAM bytes are the values that are used in the operation of the instrument These bytes are transferred from ROM to RAM when 1 the unit is first calibrated 2 if the RAM data is found to be corrupted or 3 by a request to Recall Factory Cal in the calibration menu Only the bytes that are stored in RAM may be modified by the end user in the calibration procedure The procedure for the adjustment of these calibration bytes is detailed here The calibration bytes are
47. s zero Recalled data was corrupt Delay range error Delay linkage error Wrong mode for the command Value is outside allowed range Wrong number of parameters Unrecognized command Om ND R CU a Bit 6 This bit is set if the RC recall stored settings command finds that the stored values have been corrupted A checksum is done on the settings when they are stored and if the computed checksum on recall does not match then the command is aborted and this error bit is set Bit 5 This bit is set if an attempt is made to set a delay to a value below zero or above 999 999 999 999 995 seconds Because the delay channels may be linked to each other changing a delay to an allowed value may cause another delay to exceed the allowed range of values Bit 4 This bit is set if an attempt is made to link delays in an illogical fashion For example A B 1 000 and B A 2 000 is a condition which clearly cannot be satisfied Bit 3 This bit is set if the instrument is not in the correct mode for the command that was sent For example if the instrument set to trigger on the internal rate generator the SS single shot command will be ignored and cause bit 3 to be set Bit 2 This bit is set if the value of a parameter exceeds the allowed range for that parameter For example if the command TL 20 0 is sent the command will be ignored and bit 2 will be set because the trigger level may only be set between 2 56V DC Bit 1 This
48. thout redoing the calibration To recall the factory calibration values hold down the BSP key and press the RECALL key The message Rcl Fact Cal EXC will appear Now press the EXC button to recall the factory calibration parameters Trigger Threshold Calibration The trigger threshold calibration is required only if the Ext Trigger input was damaged and the input JFET transistor Q114 has been replaced This calibration adjusts the input offset for the trigger input to cancel variations in the gate to source voltage between JFETs Recall default instrument settings by RECALL 0 EXC Select Ext trigger and set the Trigger Input to 50 Q leave the Threshold 1 00 VDC Slope Apply a 10 KHz 0 to 1 00 VDC pulse to the Ext Trigger Input Adjust the Trig Threshold value the last item in the BSP GPIB Menu so that the TRIG LED blinks intermittently Optional 1 ppm Internal Timebase Calibration This procedure should be done only if the 03 optional 1ppm TCXO oscillator is installed refer to the rear panel serial number tag There is no adjustment for the standard 25ppm time base Set the rear panel 10 000 MHz source switch to the INT position Attach a frequency counter to the 10 0 MHz reference output BNC This output can provide a 1V p p output into a 50Q load Press the STORE Menu Key and adjust the value to set the reference frequency to 10 000000 MHz 1Hz This calibrates the internal time base to 0 1ppm C
49. til 800 ns after the longest delay PULSE OUTPUTS There are four pulse output BNC s AB AB CD and CD The AB output provides a pulse for the interval between the time set for channel A and channel B The CD output provides a pulse for the interval between the time set for channel C and channel D These outputs allow the DG535 to generate two precisely timed complementary pulses OPTION 06 TRIGGER INHIBIT INPUT If the DG535 was ordered with the option 06 there will be a BNC connector located directly under the power button on the front panel to which the trigger inhibit input is applied This input is active low and is used to disable the trigger mode A TTL low inhibits triggers while a TTL high permits triggers If there is no input signal the input floats high and all triggers are enabled REAR PANEL FUNCTIONS POWER ENTRY MODULE The power entry module is used to fuse the line select the line voltage and block high frequency noise from entering or exiting the instrument Refer to the section at the front of this manual Figure 1 DG535 Rear Panel for instructions on selecting the correct line voltage and fuse IEEE 488 STD PORT The 24 pin IEEE 488 rear panel connector allows a computer to control the DG535 The command syntax for the GPIB transactions is detailed in the programming section of this manual The address of the instrument on the GPIB is set from the front panel by the GPIB menu 10 000 MH
50. z REFERENCE Internal or external references may be used as the timebase for the digital delays If the internal timebase is to be used the rear panel switch should be in the INT position In this position the 10 000 MHz internal timebase will be appear as a 1V p p square wave at the rear panel BNC This output is capable of driving a 50Q load and may be used to provide the same timebase to several DG535 s An external reference may be applied to the DG535 by placing the switch in the EXT position A 10 0 MHz 1 reference with a 1 Vp p amplitude must be applied to the rear panel BNC which now serves as a reference input If the external reference has insufficient amplitude or is more than a few percent off the nominal 10 0 MHz then the message Ext Clk Error will appear on the LCD until the problem MADE IN U S A WARNING NO USER SERVICEABLE PARTS INSIDE REFER TO USER MANUAL FOR SAFETY NOTICE FOR USE BY QUALIFIED LAB PERSONNEL ONLY OPTIONAL OUTPUTS is remedied To use the timebase in one DG535 as the timebase for several DG535 s set the switch on the master unit to the INT position Use coax cables to daisychain the 10 000 MHz output from the master unit to the other DG535 s whose switches are all set to the EXT position Use a 50Q terminator to terminate the 50Q line at the last unit on the daisychain OPTION 02 32 Volt Rear Panel Outputs If the DG535 was ordered with the option 02 there will be five re
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