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1. Base diffused resistor Base pinch resistor Separation region O Vy o Separation region Ou Resistor Epitaxial layer P type diffusion itea n diffusion layer electrode R R P type diffusion y a layer Gr E Resistor Pinch electrode Separation A va E electrode region A region J CET 4 7 R SS T 7 Y D P type substrate Figure 2 3 Structure of Capacitor Junction capacitor MOS capacitor Separation region op Separation region Oxide o o yf electrode pe SS Separation region P type substrate P type substrate There is a point to heed in applying power supply ICs It is that a method known as junction separation is used as the method of electrically separating each of the elements above By connecting a separation region so that it is formed by a P type semiconductor and is the same lowest potential as the substrate the element region and the separation region are electrically separated and insulated by being in PN junction reverse bias states If for some reason the potential of this separation region becomes a higher potential than the element region for example the NPN transistor collector region in Figure 2 1 normal operation cannot be expected since the PN junction enters a forward bias state and the separation state between the elements cannot be maintained For example when using a positive output three terminal regulator the GND pin always must be made a lowe2. cecceeeeeeseeeeeeeeeeeeeeneeeeeeeeeeeeeeeeeeeeeeeeeeseieeesneeeeeeaeenea 12 POWER SUPPLY IC APPLICATION CIRCUITS 00 ccccssccecessseeeenssseeeseseseeeenseeeeeeeseseeneenessenes 13 4 1 Typical Circuit GONNE O t a a a a a a e a a a e a aa ra ai a 13 4 2 Application COU O OT E a Taa a e A O aE R Ea e aaa 17 PRECAUTIONS ON APPLICATION c s cccessseceeeseseeeenseneeeenseeeeenseaeeeenseaeeeenseeeeseseeeenenseenenes 22 5 1 Shorting Input Pins and Ground PINS ccceeceeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeaeeeeaeeeeaeeeseeeeneeeeeeeeneeeeieeeesiaeeeeeeeee 22 5 2 sElOating Grounds TEE 22 5 3 Applying Transient Voltage to Input Pims eee ee eeeeeeeeeneeeeeeneeeeeenaeeeeeeaeeeeeeaeeeeeeaeeeeeeaaesereneeeeeeeenaeeeenas 23 5 4 Reverse Bias Between Output Pin and GND Pm 23 5 5 Precautions Related to Low Saturation Types cecceeecceseeeeeeeeeseeeeeeeeseeeeeeeeeseaeeeaeeteaeesneeeseaeesneeeneeeeene 24 5 6 Thinking on Various Protection Cirouits 24 POWER SUPPLY IC DATA SHEET APPEARANCE AND DESIGN METHODG 24 6 1 Absolute Maximum RattingS ccceeecceceseeceeeeseneeeeseneesenencenesseneesesenseseeeseeesseeeeseseeeeseneeaeeseseaeeeesesensenenees 24 6 2 Recommended Operating Conditions cceesceeseeeeeeeeceeeeeeeeeeeaeeeeeeeseaeeeeeeeseaeeeeeeeseaeeeeeeessaeeteeeeeeteaeenea 24 6 3 Electrical Specifications 6 224 nyse ne dahon dee deg een dls vec SEENEN ee ed 25 6 4 Design Method CEEE TE EAE A
3. 1 a VREF Ri Table 4 1 shows the relationship between typical output voltages and Re Table 4 1 Settings of Output Voltage Setting Resistor R2 Output Voltage Vo V Re Setting Q Note TYP values lt 3 gt Low saturation type The standard method of use is the same as for a general fixed output voltage type see Figure 4 1 However the capacitor connected to the output must have a greater capacity than in a general power supply IC In addition note that the output voltage cannot be adjusted by inserting a resistor or the like in the GND pin as described later User s Manual G12702EJ8VOUM00 4 2 Application Circuit Set This circuit set mainly is filled in for positive output voltage three terminal regulators However the circuits also can be applied to negative voltage three terminal regulators by changing the polarity of parts employed 1 High output current circuit Drives the base of an external transistor using a three without short circuit protection terminal regulator Here R1 is determined as follows Ri Ve IREG MAX Ve lo hre1min IREGMAX ES IREG MAX 4 2 1 In this circuit the output current has an actual range that is 5 to 6 times the three terminal regulator rating 2 High output current circuit This is an expansion of circuit 1 Current detection is with short circuit protection performed using Re Therefore since the current at Q is restricted b
4. B and recalculate An example of heatsink design is shown next User s Manual G12702EJ8VOUMO00 29 lt 1 gt lt 2 gt lt 3 gt Design objectives Positive power supply using uPC7805AHF Maximum output current lo max 0 6 A Maximum voltage difference between input and output VIF max 6 V Maximum operating ambient temperature Ta max 60 C Maximum junction temperature Tu max 100 C Heatsink thermal resistance calculation In a used state the junction temperature Ty is the following Tie Rihej festsetze siehe igh nef as bead aa e eS eid itl eee 6 3 Duo Thermal resistance junction to case us Thermal resistance case to heatsink 64s Thermal resistance of heatsink Po Power dissipation Here Tu max 100 C Ta max 60 C c Hs lt lt 1 C W and Rthi c 5 0 C W By substituting Pp max VDIF max x lo max 3 6 W in expression 6 3 find the thermal resistance 64s needed in the heatsink Ts Ta Pp OHS Riny c Ons SE EE 6 4 Determination of size of heatsink From expression 6 4 the design objectives can be satisfied using a heatsink of 6 1 C W Figure 6 5 shows the relationship between the thickness surface area and thermal resistance of an aluminum board By using a 3 mm thick 60 cm aluminum board here it can be seen that the heatsink will have the necessary thermal resistance Use example without heatsink The junction temperat
5. Specifications NEC guarantees the minimum values and maximum values of electrical characteristics at the time of shipment Therefore whether or not it is possible to satisfy the specifications of the power supply to be designed must be determined by adequately investigating each rating and condition in each item of the electrical characteristics Each item of the electrical characteristics is described below Since the explanations below are mainly for positive output power supply ICs reread them while reversing polarities for negative power supply ICs lt 1 gt Output voltage Vo This item is the most important rating in using a power supply IC Pay attention to measurement conditions If power supply specifications are within this range of conditions the expected precision for example 5 is obtained see Figure 6 1 Figure 6 1 Output Voltage Conceptualization For uPC7805AHF Guaranteed Range Inside Broken Lines 5 4 5 2 O gt o D 50 CO gt 5 a 5 O 4 8 Vn 10V lo 5 mA 50 0 50 100 150 Junction temperature Tu C lt 2 gt Line regulation REGin When the input voltage increases the output voltage also increases This item shows how much the output voltage changes when the input voltage Vin is varied within the measured conditions As shown in Figure 6 2 output voltage changes nearly linearly with respect to input voltage Th
6. on chip overcurrent protection circuits limiting circuits for securing SOA and overheat protection circuits are very difficult to destroy in their normal operating state Nonetheless you should not design circuits that put too much confidence in these protection circuits These protection circuits are for protection against sudden accidents To the best of your ability avoid operating protection circuits for long stretches of time In particular be careful using the overheat protection circuit since this is like operating at a temperature exceeding the absolute maximum rating 6 POWER SUPPLY IC DATA SHEET APPEARANCE AND DESIGN METHODS 6 1 Absolute Maximum Ratings This item shows values that must not be exceeded even momentarily under any usage conditions or test conditions Moreover it is a mistake to think that use at the absolute maximum ratings is possible Design should be performed so that even in an abnormal state the equipment being considered leaves room for the absolute maximum ratings In addition it is assumed that GND is the lowest potential in the case of a positive output power supply and that INPUT is the lowest potential in the case of a negative output power supply see chapter 2 6 2 Recommended Operating Conditions If used under these conditions it is possible to obtain output voltage precision as expected Think of this as a criterion for selecting a power supply IC 24 User s Manual G12702EJ8VOUM00 6 3 Electrical
7. stage transistor 0 7 V x 2 1 4 V A low saturation type power supply IC makes it possible to operate with a small voltage difference between input and output by using a PNP transistor as the output stage transistor refer to Figure 3 7 Figure 3 7 Differences Between General Power Supply IC and Low Saturation Type Output Stage Configurations a General power supply IC b Low saturation type power supply IC IN O V O OUT INO E OUT ole V es A O o GND O GND Configurations other than this are nearly identical to a general power supply IC Figure 3 8 shows a block diagram 12 User s Manual G12702EJ8VOUM00 Figure 3 8 Low Saturation Type Block Diagram O INPUT ene circuit or securing Ge SOA a Series path transistor circuit e Drive PNP type circuit OUTPUT yeaa protection H circuit E Overcurrent restriction circuit 2 S GND 4 POWER SUPPLY IC APPLICATION CIRCUITS 4 1 Typical Circuit Connection lt 1 gt Fixed output voltage type Figure 4 1 shows an example of a typical circuit connection Check the data sheet for each product type for the values of input and output capacitors Di INPUT O Cn iq Three terminal regulator Cin OUTPUT O D2 Co D1 D2 User s Manual G12702EJ8VOUMO00 Figure 4 1 Example of Typical Circuit Connection Single Power Supply Output If the wiring from a
8. voltage circuit which determines the output voltage of the power supply IC is an extremely important part within the circuit The method for configuring this circuit is as follows e Band gap reference method Use the forward characteristic between the base and emitter of the transistor The possibility of making the reference voltage 2 V or less is a feature of this method Figure 3 2 shows the principles of the band gap reference method Figure 3 3 is a simple circuit diagram of the band gap reference reference voltage used in the uPC7800A Series Figure 3 2 Band Gap Reference Circuit V l Re KT jp Re 8 Vrer VBes Rs q In el VE A O A Ri Re as AVBE o E aor g E VBE as oe R3 e k O GND The reference voltage is as follows Vrer Vees Ic2 lB3 R2 Re Vees AVBE IB3 R2 R3 R2 KT Ste KI pB EEEE EE dE EE IEA E EERTE EAE EEE IEA E AENEA TE 3 3 31 q Ri The temperature coefficient is as follows aper Wees K R2 R2 e In oT oT q Pa Ri By optimally choosing the ratio of P2 gone a temperature compensated reference voltage is known to be obtained Rs D User s Manual G12702EJ8VOUM00 Figure 3 3 Simplified Band Gap Reference Circuit of uPC7800A Series O Vin VREF rk GE lt 2 gt Error amplifier Oo GND This circuit controls the output voltage by detecting and comparing the reference voltage created b
9. NEC User s Manual Usage of Three Terminal Regulators Document No G12702EJ8VOUMOO0 8th edition Date Published May 2000 N CP k NEC Corporation 2000 Printed in Japan MEMO 2 User s Manual G12702EJ8VOUM00 The application circuits and the circuit constants in this document are only examples and not intended for use in the actual design of application systems for mass production e The information in this document is subject to change without notice Before using this document please confirm that this is the latest version e Not all devices types available in every country Please check with local NEC representative for availability and additional information e No part of this document may be copied or reproduced in any form or by any means without the prior written consent of NEC Corporation NEC Corporation assumes no responsibility for any errors which may appear in this document e NEC Corporation does not assume any liability for infringement of patents copyrights or other intellectual property rights of third parties by or arising from use of a device described herein or any other liability arising from use of such device No license either express implied or otherwise is granted under any patents copyrights or other intellectual property rights of NEC Corporation or others e Descriptions of circuits software and other related information in this document are provided for illustrative purposes in semiconduct
10. arate circuit is needed to perform power supply overheat protection 3 2 Operating Principles of Adjustable Output Types An adjustable output type uPC317 uPC337 differs from a fixed output voltage type in that it uses a method for configuring an output voltage setting voltage circuit externally so that an arbitrary output voltage can be set externally Figure 3 6 is the block diagram of a variable output voltage type The output voltage is controlled by comparing the voltage between external resistors Ra and Rs and the reference voltage Vrer in the error amplifier Moreover each block is connected between INPUT and OUTPUT and the current needed in each block circuit operating current is output from the OUTPUT pin Therefore the outflow current from the ADJ pin becomes negligible and its affect on the output voltage value can be ignored User s Manual G12702EJ8VOUMO00 11 Figure 3 6 Adjustable Output Type Block Diagram O INPUT Current Protection source circuit Startup circuit OUTPUT Reference voltage source VREF KBJ Re Ke Q setting Vo Ra circuit 3 3 Operating Principles of Low Saturation Types All of the power supply ICs discussed so far use Darlington connected NPN type transistors in the output stage Therefore the voltage difference between input and output that is needed to operate these power supply ICs cannot be lower than the voltage between the base and emitter of the Darlington connected output
11. ary They prevent output voltage pulldown due to discrepancies in the startup timing of each regulator 15 Wired OR Vun D1 Vout co G D2 Vine Ds Da When connecting the outputs of two or more three terminal regulators do it so that voltage from outside is not added to the regulator output at D and Ds D2 and D4 are connected to compensate for the lowering of output by D and Ds User s Manual G12702EJ8VOUM00 21 5 PRECAUTIONS ON APPLICATION Do not use a three terminal regulator under temperature conditions or voltage conditions that exceed the ratings Other precautions that are specific to three terminal regulators are shown below 5 1 Shorting Input Pins and Ground Pins When a capacitor with a large capacity is connected to the load of a three terminal regulator if the input pin is shorted to GND or the power supply is turned OFF the voltage of the capacitor connected to the output pin is applied between the output and input pins of the three terminal regulator Figure 5 1 a b Discharge current Vout The withstand voltage between the output and input pins of a three terminal regulator is approximately 0 7 V fora low current with the output transistor base emitter voltage Therefore a diode like the one in Figure 5 1 b is effective against the reverse bias of the input and output pins Figure 5 1 b is for a positive voltage regulator The diode direction is reversed for ne
12. ax 044 548 7900 Fax 02 528 4411 Europe Technical Documentation Dept Fax 49 211 6503 274 South America Taiwan NEC do Brasil S A NEC Electronics Taiwan Ltd Fax 55 11 6465 6829 Fax 02 2719 5951 would like to report the following error make the following suggestion Document title Document number Page number If possible please fax the referenced page or drawing Dota Excellent Acceptable Clarity Technical Accuracy Organization
13. can be no lower than the sum of the output saturated voltage of the PC ZA and the output voltage of the three terminal regulator A tracking regulator is configured using a power transistor with one positive voltage three terminal regulator The positive voltage is the fixed voltage of the three terminal regulator The negative voltage can be changed arbitrarily by the split ratio of Ri and Re Thus the negative voltage output is as follows D protects against reverse bias between the base and emitter of the transistor at power on 20 User s Manual G12702EJ8VOUM00 13 Tracking regulator circuit Vout Ri uPC741 E Re Re Vout This power supply has superior tracking characteristics due to using an op amplifier and one positive and one negative voltage three terminal regulator The GND pin of each three terminal regulator is driven in common by the op amplifier output Favorable tracking characteristics are obtained by making Ri Re Moreover bias current errors also can be canceled if the resistor R1 Rz is added between the non inverting pin of the op amplifier and GND 14 Positive and negative dual power supply circuit using positive voltage three terminal regulators This is a positive and negative dual power supply that uses two positive voltage three terminal regulators D and Dz are low forward voltage diodes that are absolutely necess
14. cuit for a single power supply load these sometimes are needed depending on circuit conditions Dit Dit Absolutely necessary for loads shown by solid lines in which a load current flows from Vout toward Nour This is to prevent regulator output on either side from being latched down by differences occurring in the rise of regulator output voltage due to smoothing circuit capacitor capacity differences or the like Note that these are not specifically needed in the case of only those loads shown by dashed lines Di2 Dei As in the sample circuit for a single power supply load these sometimes are needed depending on the application circuit 14 User s Manual G12702EJ8VOUM00 If the output pin becomes a lower potential than GND the P type separation region and n type output pin NPN transistor enter a forward bias state and the parasitic transistor shown with dashed lines is formed When this occurs it is connected to the adjacent transistors and does not operate normally Figure 4 3 Example of Power Supply IC Cross Section Diagram Latchdown Separation Output O region NPN transistor NPN transistor p Ge lt 2 gt Adjustable output voltage type When a voltage not included in a fixed output voltage type is needed or the output voltage is to be adjusted and used even a fixed output voltage type can be used by floating the GND as described later but voltage precision and drift become a problem A
15. d Limiting Circuit for Securing SOA uPC7800A Series Limiting circuit for securing SOA e INPUT TON S I l l 27T l l 7 Ki l A I A Sa ee 1 Qis Say N Ki e Ss Q171 2 I Sg FA SLL Ub Output stage transistor a Qis Current limiting transistor R11 Current detection resistor A O OUTPUT User s Manual G12702EJ8VOUM00 lt 8 gt Overheat protection circuit The overheat protection circuit prevents destruction of the IC by cutting off output if the temperature of the chip itself increases too much Figure 3 5 shows the parts of an overheat protection circuit Q12 which is biased to the extent that it is not ON in a normal operating state is completely ON at 150 C to 200 C accompanying a decrease in Vse when the temperature of the chip increases When Qiz is ON it cuts off the output voltage by absorbing the base current of the output stage power transistor Figure 3 5 Example of Overheat Protection Circuit uPC7800A Series O INPUT La a kK ao O OUTPUT GE Q12 Overheat protection transistor D O GND The overheat protection circuit is designed to operate at temperatures exceeding the absolute maximum rating generally 150 C Therefore if the overheat protection circuit has operated the IC should be considered to have been exposed to an abnormal state and positive use of the overheat protection circuit should be avoided so a sep
16. dasdapecsnscajaagdechesaastapaaiacsapeusieped bee T 28 User s Manual G12702EJ8VOUMO00 1 INTRODUCTION NEC produces a variety of ICs for power supplies that differ in their on chip functions and usage Within these large quantities of three terminal regulators have come to be used to configure stabilized power supplies easily using few external components However the occurrence of unexpected irregularities when designing power supply circuits also has increased Therefore this manual starts with the basic structure of the main bipolar process that is used in ICs for power supplies and gives precautions pertaining to actual applications 2 BASIC STRUCTURE OF A POWER SUPPLY IC As mentioned in chapter 1 a power supply IC mainly uses a bipolar process Understanding the structure of an IC that uses a bipolar process also is useful for applications 2 1 Structure of a Bipolar IC The following elements can be made into an IC in a general bipolar process NPN transistor PNP transistor Resistor Capacitor Figures 2 1 through 2 3 show the structure of each Figure 2 1 Structure of NPN Transistor and PNP Transistor NPN transistor PNP transistor Separation region Separation region si Separation region Collector Base Emitter a p_Collector p_ Emitter Pa L 1 1 L 1 1 I 1 e X De n A A Tz P type substrate User s Manual G12702EJ8VOUMO00 Figure 2 2 Structure of Resistor
17. erefore it is possible to infer how much the output voltage will change from the initial period when the initial input voltage is changed to a given input voltage User s Manual G12702EJ8VOUMO00 25 26 Figure 6 2 Line Regulation REGin Conceptualization For uPC7805AHF Vin 10 V Standard 30 20 10 REGin TYP x lt lt x z M a Input stability REGin mV 10 Ta 25 C lo 500 mA 0 5 10 15 20 25 Input voltage Vin V lt 3 gt Load regulation REGL Whereas REG is the change in output voltage with respect to input voltage load regulation REGL shows the change in output voltage with respect to load current output current When load current increases output voltage decreases nearly linearly The output voltage for an arbitrary load current can be inferred in the same way as REGin see Figure 6 3 User s Manual G12702EJ8VOUM00 Figure 6 3 Load Regulation Conceptualization For uPC7805AHF lo 500 mA 10 I PA 0 Z S 2 5 S rm m sg T a0 F A g 8 oc wn Ki 2 1 5 20 T 30 Ta 25 C Vin 10V 0 0 5 1 0 1 5 Output current lo A lt 4 gt Quiescent current IBias This is the bias current needed for each internal block of a power supply IC to operate It flows from input toward GND Applications that adjust output voltage by i
18. gative voltage 5 2 Floating Ground Pins Do not make the GND pin of a three terminal regulator floating in the operating state If it is made floating an input voltage that has not been stabilized is output unchanged This is because the output stage power transistor is biased by an overvoltage protection Zener or current mirror transistor leakage current Since IC internal overheat protection and the like do not operate normally in this case there is a possibility of destruction if the load is short circuited or on an overload Be particularly careful when using a socket 22 User s Manual G12702EJ8VOUM00 5 3 Applying Transient Voltage to Input Pins A three terminal regulator is destroyed if a higher voltage than the rating or a voltage more than 0 5 V lower than the GND pin is applied to the input line In cases in which such voltages are superimposed on the line add a surge suppressor using a Zener diode or the like Figure 5 2 a b 5 4 Reverse Bias Between Output Pin and GND Pin Figure 5 3 a b External protection diode In the sample application shown in Figure 5 3 a the voltage of the Zener diode is applied between the output and GND pins of the three terminal regulator when the load is short circuited Inside the three terminal regulator a diode like that shown in Figure 5 3 b apparently is formed but if a current flows in this part the three terminal regulator is sometimes destroyed Therefore when u
19. he capacitor is connected in parallel Radiation design The junction temperature can be calculated using the following expression ze Rhi OCHS k OS APDR TA geegent Eeer ae Dee ce ee 6 1 Duo Thermal resistance junction to case Ouer Contact thermal resistance includes thermal resistance of insulation sheet when using insulation sheet Gs Thermal resistance of heatsink Po Internal power dissipation of IC Pp VIN Vo lo Vin IBias TA Operating ambient temperature Expression 6 1 is the calculation expression when using a heatsink When not using a heatsink such as in the uPC78L00 Series use the following expression RE PD Tastee ible aires ee eee ei eet 6 2 Dua Thermal resistance junction to ambient air Use the values in the data sheets for Rinu c and Rihw a in expressions 6 1 and 6 2 Since Ty Rtnw c Po and Ta are given find the thermal resistance of the heatsink Oz from them using expression 6 1 Figure 6 5 shows the thermal resistance of an aluminum board Since the heatsink manufacturer produce heatsinks suited to power supply ICs also consult the heatsink manufacturer Figure 6 5 Thermal Resistance of Aluminum Board Thermal resistance of heatsink Ous C W E 1 10 20 50 100 200 500 1000 Surface area of heatsink A cm If Tu is not within the design values return to A or
20. n adjustable output voltage type is useful in such cases Figure 4 4 shows an example of the typical connection Since a bias current for the operation of each block inside the IC flows from INPUT to OUTPUT as described in section 3 2 be careful of the load current By selecting 240 Q as R1 as in the sample typical connection even when there is no load no problems arise since a current of 1 25 V 240 Q 5 2 mA flows to OUTPUT User s Manual G12702EJ8VOUMO00 15 16 Cin Co Caps R1 R2 Figure 4 4 Example of Typical Connection Circuit Adjustable Output Power Supply Note This example is for a positive voltage For a negative voltage uPC337 D and capacitor polarity are reversed Since there may be oscillation if the wire leading from a smoothing circuit to a three terminal regulator is long 15 cm or more add a capacitor near the input pin For an application in which the load current changes suddenly add a 10 uF or more capacitor for output voltage transient response improvement and add 10 uF to Cans at the same time Connecting a 10 uF capacitor parallel to Re can improve the ripple rejection rate approximately 20 dB and increase oscillation stability In this case diode D1 is needed for to prevent application of backward voltage on an output short circuit These are resistors for setting the output voltage The output voltage Vo is determined as follows vo 1 Fe e VREF lapu R2
21. ng c Spring washer Heatsink beer Heatsink m Flat washer SM nut e Spring washer Ik 3Mnut MP 45G TO 220 Table 6 2 Recommended Insulating Bushings and Insulating Board Code No Product Name Quality of Materials Incombustibility ae Insulating bushing 25K bushing U Gelanex 3310 Light brown UL 94V 0 Insulating board MP 25 insulating board A Polyester Colorless transparent Sege User s Manual G12702EJ8VOUMO00 31 MEMO 32 User s Manual G12702EJ8VOUM00 MEMO User s Manual G12702EJ8VOUM00 33 MEMO 34 User s Manual G12702EJ8VOUM00 NEC Although NEC has taken all possible steps essage to ensure thatthe documentation supplied to our customers is complete bug free and up to date we readily accept that From errors may occur Despite all the care and precautions we ve taken you may Name encounter problems in the documentation Please complete this form whenever Company you d like to report errors or suggest improvements to us Tel FAX Address Thank you for your kind support North America Hong Kong Philippines Oceania Asian Nations except Philippines NEC Electronics Inc NEC Electronics Hong Kong Ltd NEC Electronics Singapore Pte Ltd Corporate Communications Dept Fax 852 2886 9022 9044 Fax 65 250 3583 Fax 1 800 729 9288 1 408 588 6130 Korea Japan NEC Electronics Hong Kong Ltd NEC Semiconductor Technical Hotline DE ees eee OMAE tech F
22. nserting a resistor in GND take this item into account lt 5 gt Quiescent current change Alsias This shows the change in Isias when the input voltage or load current changes lt 6 gt Ripple rejection rate ReR The ripple voltage that appears in the output when a 120 Hz sine wave minimum value and maximum value of sine wave are noted in measured conditions is input in the input is represented by the following expression R R 20 log Vin Vorippie dB If the frequency increases R e R decreases mainly due to the frequency characteristics of the internal error amplifier of the IC lt 7 gt Output noise voltage Vn This shows the noise that occurs inside a power supply IC mainly thought to be thermal noise User s Manual G12702EJ8VOUMO00 27 lt 8 gt lt 9 gt Peak output current lopeak This is the current at which the overcurrent protection circuit operates It is defined as the output current when the output voltage is lowered by 2 from its initial value As described in chapter 3 the overcurrent protection circuit operates together with the stable operation area Moreover note that lopeak decreases as temperature increases negative temperature characteristic Figure 6 4 shows the lopeak Vin Vo characteristics of the uPC7800A Series For a nonlinear load such as a motor or lamp select a power supply IC that has sufficient leeway 50 or less of normal characteristic graph Output short circuit current loshort Thi
23. nsportation equipment automobiles trains ships etc traffic control systems anti disaster systems anti crime systems safety equipment and medical equipment not specifically designed for life support Specific Aircraft aerospace equipment submersible repeaters nuclear reactor control systems life support systems or medical equipment for life support etc The quality grade of NEC devices is Standard unless otherwise specified in NEC s Data Sheets or Data Books If customers intend to use NEC devices for applications other than those specified for Standard quality grade they should contact an NEC sales representative in advance M7D 98 12 User s Manual G12702EJ8VOUM00 3 CONTENTS INTRODUGTION BEE 5 BASIC STRUCTURE OF A POWER SUPPLY IC ccccsseecessseeeeeseseeeeseseeeeeseseeeeessscenensseenes 5 2 1 Struicture ofa Bipolar 1G e a Te a e e aara E aaa a a dase shag cusastngicansacaasagraaadegassieussiseudtuniedeseaeesbeianae 5 2 2 About Power Supply IC Equivalent Crcufts ccc eeeceeeseeceeeeeeneeeeeeseeeteaeeseaeeseaeeseaeesnaeeseeeseaeeseaeeseeeene 6 BASIC CIRCUITS OF A POWER SUPPLY IC cc cccccsseeeeeeseceeeeeseensesesceeseseseeeeeseseensesesnenes 7 Bal Basi CirCuits geesde ee ide Mates eee elie ei eege See tay 7 3 2 Operating Principles of Adjustable Output Types ccceeeeeseeeeeseeeeeeeeeeeeeeeeeeeneeeeeeeeeeeteeeeeeeeieeeeneeeeeeee 11 3 3 Operating Principles of Low Saturation Types 0
24. or product operation and application examples The incorporation of these circuits software and information in the design of the customer s equipment shall be done under the full responsibility of the customer NEC Corporation assumes no responsibility for any losses incurred by the customer or third parties arising from the use of these circuits software and information While NEC Corporation has been making continuous effort to enhance the reliability of its semiconductor devices the possibility of defects cannot be eliminated entirely To minimize risks of damage or injury to persons or property arising from a defect in an NEC semiconductor device customers must incorporate sufficient safety measures in its design such as redundancy fire containment and anti failure features e NEC devices are classified into the following three quality grades Standard Special and Specific The Specific quality grade applies only to devices developed based ona customer designated quality assurance program for a specific application The recommended applications of a device depend on its quality grade as indicated below Customers must check the quality grade of each device before using it in a particular application Standard Computers office equipment communications equipment test and measurement equipment audio and visual equipment home electronic appliances machine tools personal electronic equipment and industrial robots Special Tra
25. r potential than the potential of other pins 2 2 About Power Supply IC Equivalent Circuits Equivalent circuits that are shown in data sheets are so designated assuming the premise of the preceding section that separation regions and substrate are made the lowest potential Be careful not to reference these when this premise is violated User s Manual G12702EJ8VOUM00 3 BASIC CIRCUITS OF A POWER SUPPLY IC 3 1 Basic Circuits Although the basic circuits that make up a power supply IC differ according to the product type the following elements are necessary lt 1 gt Reference voltage circuit lt 2 gt Error amplifier lt 3 gt Active load constant current circuit lt 4 gt Output stage power transistor lt 5 gt Startup circuit The following protection circuits also are on chip lt 6 gt Overcurrent protection circuit lt 7 gt Limiting circuit for securing safe operating area SOA lt 8 gt Overheat protection circuit Figure 3 1 shows a block diagram of a power supply IC Figure 3 1 Power Supply IC Block Diagram oO INPUT Y Y Y Current Protection source te circuit e y Series bus Startup Reference transistor circuit voltage YA so O OUTPUT Error amplification circuit Re Split resistor Ra 7r GND User s Manual G12702EJ8VOUMO00 The operation of each block is explained in simple terms below lt 1 gt Reference voltage circuit The reference
26. rates the rise time of the output voltage At power on this is the three terminal regulator s specific output voltage after which it gradually rises to its final value The initial output voltage is Vo1 VoreG The output voltage after stabilization is Vompoe Vos Vorec R1 D 2 Furthermore the delay can be represented as follows if expecting up to 99 of the final value T CH In 0 01 s 4 10 The Zener diode in the circuit shown in 5 is replaced by a resistor V Vout VoreG Rit D Use a voltage difference between input and output that is within the three terminal regulator ratings For a load short circuit or capacity load the diode shown using dashed lines is needed and in particular a low forward voltage is needed User s Manual G12702EJ8VOUM00 10 Adjustable output voltage circuit 0 5 to 10 V without short circuit protection uPC7805A RD6 2EB 11 Adjustable output voltage circuit 7 to 30 V 12 Tracking regulator circuit Vin O uPC741 Splits the fixed output voltage Voreq of the three terminal regulator using R4 and Rs and compares with the output voltage Vout value split using H and Re The output voltage can be represented as follows This is similar to the circuits shown in 5 and 8 Since it uses op amplifier uPC741 with a single power supply the lowest value of the output voltage
27. s is the current that flows when output is short circuited Since most NEC power supply ICs have an on chip limiting circuit for securing SOA the following relation holds loshort lt lopeak Like lopeak loshort displays a negative temperature characteristic Refer to Figure 6 4 for temperature characteristics of the output short circuit current and changes with respect to input voltage Figure 6 4 Example of lopeak Characteristics uPC7800A Series lopeak Vin Vo characteristic Peak output current lopeak A 0 5 10 15 20 25 30 35 Voltage difference between input and output Vin Vo V 6 4 Design Methods 28 A Input circuit design Determine the capacity of a smoothing capacitor of an input circuit using an O H Shade graph or simulator so that the minimum value of the input voltage is not lower than the measurement conditions of output voltage At this time connect a film capacitor between input and GND of the power supply IC separate from the smoothing capacitor to prevent abnormal oscillation refer to the data sheet of each product type for capacitor values User s Manual G12702EJ8VOUMO00 B C Output circuit design Check whether the load current used is a current no greater than the peak output current Connect a capacitor for abnormal oscillation prevention between output and GND of the power supply IC If transient load stability becomes a problem make sure t
28. sing a GND like that shown in Figure 5 3 a in a floating state it is necessary to add a low forward voltage diode from the GND pin of the three terminal regulator toward the output pin User s Manual G12702EJ8VOUMO00 23 5 5 Precautions Related to Low Saturation Types Since a low saturation type of power supply IC uses a PNP transistor in the output stage particular care is needed In a low input state before the output voltage enters regulation state such as at startup a large circuit current flows because the output stage transistor is saturated Depending on the product the circuit current is decreased at startup by an on chip rushing current prevention circuit but even in this case a relatively large circuit current flows compared to normal operation For details refer to the Circuit operating current at startup IBias s rating of each product Thus care is needed in the following matters e On startup be careful of the output capacity of the power supply on the input side and the output impedance since a circuit operating current flows in the input superimposed on the load current e tis not possible to adjust the output voltage by inserting a resistor or the like in the GND This is because the circuit operating current increases at startup Be sure to connect a low impedance type capacitor to the output to increase stability against abnormal oscillation 5 6 Thinking on Various Protection Circuits NEC power supply ICs which have
29. smoothing circuit to the three terminal regulator is long there may be oscillation Therefore add a 0 1 to 0 47 uF capacitor with superior voltage and temperature characteristics near the input pin This always must be added for oscillation prevention in the case of a negative voltage three terminal regulator For an application in which the load current changes suddenly also add 10 to 100 uF of electrical capacitors for output voltage transient response improvement Although not needed for standard applications this is necessary when the time constant on the load side is long and there is a residual voltage in Co for some time after the power supply is cut and backward voltage is applied to the regulator IC Needed when there is a possibility of OUTPUT being lower potential than GND 13 Figure 4 2 is an example of a typical connection for obtaining a positive and negative power supply The diodes between output and GND are for preventing latchdown at startup and are absolutely necessary in the case of loads shown by solid lines Without the diodes current flows in the separation regions between elements as described in chapter 2 and the output voltage does not rise refer to Figure 4 3 Figure 4 2 Example of Typical Circuit Connection Dual Power Supply Output Positive voltage 3 terminal regulator Negative voltage 3 terminal Load regulator Cin Co Cin Co As in the sample cir
30. ture of the transistors is low or high Overcurrent protection circuit This is a protection circuit for preventing the load current from exceeding the current capacity of the output stage power transistor It restricts the base current of the output stage power transistor by biasing the current restriction transistor more deeply in accordance with the voltage drop in the current detection resistor inserted in the load current route Limiting circuit for securing safe operating area SOA The limiting circuit for securing SOA operates to cut down the output current if the voltage between input and output voltage between the collector and emitter of the output stage power transistor becomes large so that the safe operating area of the output stage power transistor is not exceeded If the voltage difference between input and output exceeds the breakdown voltage 7 to 8 V of a Zener diode connected between input and output it limits the base current of the output stage power transistor by biasing the current limiting transistor more deeply using the breakdown current Since the larger the voltage difference between input and output the more the base current of the output stage power transistor is limited the load characteristic is a foldback type drooping characteristic as a result Figure 3 4 shows the parts of a general overcurrent protection circuit and limiting circuit for securing SOA Figure 3 4 Example of Overcurrent Protection Circuit an
31. ure Ty in the used state when not installing a heatsink is the following dees Rin Qa ao E EE 6 5 Rinu a Thermal resistance junction to ambient air free air Po Power dissipation TA Operating ambient temperature Setting Tu to 100 C or less in the used state is recommended User s Manual G12702EJ8VOUM00 Precautions when installing in a heatsink e Make the convexity or concavity of the part installation surface of the heatsink 0 05 mm or less e Spread silicon grease to a uniform thickness between the heatsink and part Determine the kind of grease on consulting the maker of the heatsink e Painting the heatsink black increases its effectiveness in radiating heat However if it is close to a heat source it has the reverse effect of absorbing heat e Use one of the insulating board bushings shown in Table 6 2 e Cuta screw in a heatsink and absolutely do not use self tapping screws to install one When installing a heatsink if the tightening torque of a screw is too great the fins can be distorted and the IC damaged Drive screws using a torque driver that can manage the tightening torque Table 6 1 Three Terminal Regulator Tightening Torque TO 126 2 0 x 10 to 4 1 x 10 TO 220 3 1 x 10 to 5 1 x 10 MP 45G 3 1 x 10 to 5 1 x 10 Figure 6 6 Standard Installation Method for Heatsink Insulation 3M screw Flat washer e 3M screw Flat washer en L BE Insulating board l 7 Insulating bushi
32. ut voltage must be set within a range that holds the voltage difference between input and output to the ratings even on a short circuit 6 High input high output voltage circuit Note with short circuit protection Vin Qi Ri 4 7 KQ This circuit combines circuits 4 and 5 The circuit made up of Q1 Q2 and D1 is a preregulator The output voltage is as follows Vout Vo REG Van 4 7 D2 protects against reverse bias in the GND and OUT pins on a load short circuit Note Dz or ZD must be selected so that the voltage difference between input and output of the three terminal regulator is kept within ratings even on a load short circuit In addition D2 must have low forward voltage 18 User s Manual G12702EJ8VOUM00 7 Remote shutdown circuit Control ow Rs Vo final value Delay time T Power on 9 Adjustable output voltage circuit without load short circuit protection Note that applications using the adjustable output three terminal regulator uPC317 are superior in output voltage precision and stability Control the output voltage using a preregulator set up ahead of the three terminal regulator The control input is as follows At H level Normal output At L level Output interruption In addition D1 is added to prevent reverse bias between the input and output pins of the three terminal regulator This circuit mode
33. y VBE2 R2 limax the output current is as follows loqax l1 MAx IREG MAX _ VBe2 Re S TREG MAXS E 4 3 3 High output current circuit D cancels Ver at Q1 with short circuit protection Q and three terminal current distribution is determined by Ri and R2 R10 4 Q Qi H Re 22Q Rse6Q Lal Di Caution Absolutely do not connect output pins in parallel to increase the current capacity of a three terminal regulator If the output voltage becomes unbalanced certain ICs operate in a restricted current vicinity and current hardly flows in certain ICs and furthermore the current may flow in reverse Also refer to 15 Wired OR User s Manual G12702EJ8VOUM00 17 4 High input voltage circuit This circuit can be used when the input voltage exceeds the rating Vin Van REN 4 6 lout max NFE1 MIN Moreover if the load current changes little a resistor can be used 5 High input high output voltage circuit without short circuit protection Using the fact that the current flowing out from the GND pin of the three terminal regulator is practically constant add Zener Di to the GND pin to raise only the Zener portion of the voltage R supplies idling to the Zener It also is possible to use a resistor but this is inferior to the Zener from a stability standpoint D is needed as load short circuit protection In addition the inp
34. y the reference voltage circuit and the resistor split output voltage If Vout is the output voltage and Vrer is the reference voltage refer to Figure 3 1 the following relationship holds VOUT sy VBREF veseecseccccncoasscsisccccvencuscevevscersecusearsvenenecans p G A Here A is the open loop gain of the error amplifier and Ra Ra Re lt 3 gt Active load constant current circuit Expression 3 1 becomes the following if the open loop gain A of the error amplifier is sufficiently large compared to 1 Vout Vrer p A small bias current and high resistance are realized by using a constant current circuit in the error amplifier load to make A 60 to 80 dB lt 4 gt Output stage power transistor The output stage power transistor supplies current to the load Although normally a Darlington form NPN the low saturation type of power supply IC uses a PNP single transistor User s Manual G12702EJ8VOUM00 9 lt 5 gt lt 6 gt lt 7 gt 10 Startup circuit A power supply IC has an on chip constant current circuit for use as an error amplifier load or for biasing the reference voltage circuit A constant current circuit which consists of paired transistors does not begin to operate as long as the diode connected transistors are not in a steady bias state A startup circuit therefore is set up and it biases the active load at power on to cause normal operation to begin whether the tempera
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