AN-1164 LM3647 Reference Design User`s Manual (Rev. B)
Contents
1. products and applications Buyers should provide adequate design and operating safeguards TI does not warrant or represent that any license either express or implied is granted under any patent right copyright mask work right or other intellectual property right relating to any combination machine or process in which Tl components or services are used Information published by TI regarding third party products or services does not constitute a license to use such products or services or a warranty or endorsement thereof Use of such information may require a license from a third party under the patents or other intellectual property of the third party or a license from TI under the patents or other intellectual property of TI Reproduction of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties conditions limitations and notices TI is not responsible or liable for such altered documentation Information of third parties may be subject to additional restrictions Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or service voids all express and any implied warranties for the associated Tl component or service and is an unfair and deceptive business practice Tl is not responsible or liable for any such statements Buyer acknowledges and agrees th2. Vere 1 5V R1 R2 R3 R4 R3 5 1kQ R1 100kQ RS5 0 047k0 Max Current 1 09Ampere 1 6 AN 1164 LM3647 Reference Design Demonstration Board SNVA023B September 2000 Revised May 2013 Submit Documentation Feedback Copyright 2000 2013 Texas Instruments Incorporated la TEXAS INSTRUMENTS www ti com Functional Description 2 5V REFERENCE POWERSUPPLY LM7301 Figure 4 Setting the Chart Current 5 2 7 Setting Maximum Battery Voltage The resistor network see Figure 5 scales the battery voltage to a suitable level for the LM3647 For Ni Cd Ni MH batteries the network is less critical but limits the maximum battery voltage it is only used as a backup termination method For Li lon batteries the network must be more accurate requiring precision resistors with low tolerances e For Ni Cd Ni MH The dimensioning is accomplished in the following manner First calculate the maximum battery voltage for the specific battery pack See the example below Battery Voltage Cell 1 2V NumberOfCells 5 BatteryPackVoltage 1 2x5 6V 2 MaximumBatteryVoltage Cell 1 85V MaximumBatteryVoltage 1 85x5 9 25V 3 When the Maximum Battery Voltage has been determined the voltage divider network has to be dimensioned using the following formula MaximumBatteryVoltage x EL 3 0 71V R7 R6 R7 7 BATTERY_ VOLTAGE CEL Figure 5 Maximum Battery Voltage e For Li lon SNVA023B September 2000 Revised May 2
3. 3 Selection Pins SEL1 SEL2 and SEL3 SNVA023B September 2000 Revised May 2013 AN 1164 LM3647 Reference Design Demonstration Board 13 Submit Documentation Feedback Copyright 2000 2013 Texas Instruments Incorporated IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries TI reserve the right to make corrections enhancements improvements and other changes to its semiconductor products and services per JESD46 latest issue and to discontinue any product or service per JESD48 latest issue Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and complete All semiconductor products also referred to herein as components are sold subject to Tl s terms and conditions of sale supplied at the time of order acknowledgment Tl warrants performance of its components to the specifications applicable at the time of sale in accordance with the warranty in Tl s terms and conditions of sale of semiconductor products Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty Except where mandated by applicable law testing of all parameters of each component is not necessarily performed Tl assumes no liability for applications assistance or the design of Buyers products Buyers are responsible for their products and applications using TI components To minimize the risks associated with Buyers
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5. input is connected to J3 and if not used Short J8 Voltage Regulation Range Voltage regulation loop setting J14 not used with external LM317 regulation J7 slow defines maximum voltage output See also Section 7 Voltage Measurement The battery voltage is selected with the voltage jumpers J11 and J12 depending on number of cells chemistry see Figure 1 For instance a 9V Ni Cd block battery has 6 cells in it and therefore needs the jumper at Ni 6 Cells on J11 and J12 AN 1164 LM3647 Reference Design Demonstration Board SNVA023B September 2000 Revised May 2013 Submit Documentation Feedback Copyright 2000 2013 Texas Instruments Incorporated ld TEXAS INSTRUMENTS www ti com Jumper Settings Ni 4 Cells Ni 4 Cells Ni 8 Cells Ni 8 Cells Ni 6 Cells Ni 6 Cells Li 4 Cells Ni 10 Cells Li 4 Cells Ni 10 Cells Li 3 Cells Li 3 Cells Li 2 Cells Ni 5 Cells Li 2 1 Cells Ni 5 Cells Li 1 Cells J11 J12 Figure 1 Voltage Measurement 4 5 Charge Current The charge settings for LM3647 current control are shown below If the external LM317 is used to control the charge current then the jumpers J9 J10 and J13 have no relevance when using LM317 regulation mode this jumper must be placed in either position If external LM317 regulation is used then set jumper J7 to position slow for LM3647 regulation set J7 to fast 4 6 LM3647 Current Regulation The I jumper J10 is used to select between different current sense resis
6. 013 AN 1164 LM3647 Reference Design Demonstration Board 7 Submit Documentation Feedback Copyright 2000 2013 Texas Instruments Incorporated I TEXAS INSTRUMENTS Functional Description www ti com The voltage divider network for Li lon is very important If the battery voltage is scaled too low the battery will not attain its full capacity when charged and if scaled too high the battery may become damaged Never exceed the recommended maximum voltage or current for a Li lon battery The dimensioning is done in the following manner First calculate the maximum battery voltage for the specific battery pack See example below Battery Voltage Cell 3 6V NumberOfCells 2 BatteryPackVoltage 3 6x2 7 2V MaximumBattery Voltage Cell 4 1V MaximumBatteryVoltage 4 1x2 8 2V aAa Ee When the maximum battery voltage has been determined the voltage divider network has to be dimensioned using the following formula R7 MaximumBatteryVoltage x R6 R7 2 675V 2 740V if SEL3 is set to Voc 6 The LM3647 has two different regulation voltages which the user can select the 2 675V SELS tied to GND and 2 740V SEL3 tied to Vcc This selection pin can be used to configure the charger to regulate for different input voltages so that the charger can handle both 3 6V and 3 7V cells without changing the resistor values in the divider network SEL3 can also be used if there is problem in finding the right values in the resisto
7. 0k CONRA 2P 100 nF kacca l1 R21 R20 e 100k J1 2 47 nF 5V i CONRA 2P ou 15k 2 2K D2 C4 R2 K A 5V 68k R15 BAS16LT1 NC i tk ee J3 1 gt 2 5Vper TEMPERATURE lt _ DISCHARGE L gt R3 a R28 Ha NC DS 100k T LM4040A 2 5 A Figure 8 Li_lON Set To SEL1 SEL2 SEL3 Vec After charging maintenance charging until battery removal NA 4 2V Cell Hi Z After charging maintenance charging until battery removal If battery voltage Li lon NA drops below a predefined value the charger restarts the charge process GND After charging no maintenance charging is applied If battery voltage drops NA 4 1V Cell below a predefined value the charger restarts the charge process NOTE When a three chemistry charger is designed special considerations must be taken into account regarding configuration pin SEL3 This pin has different meanings when switching between Ni Cd Ni MH and Li lon To ensure correct operation the SEL3 pin MUST be tied to VCC If Li lon cells of 4 1V Cells are used then minor adjustments have to be done to the voltage measurement resistor divider 10 AN 1164 LM3647 Reference Design Demonstration Board SNVA023B September 2000 Revised May 2013 Submit Documentation Feedback Copyright 2000 2013 Texas Instruments Incorporated I TEXAS INSTRUMENTS www ti com LM3647 Reference Design Demonstration Board 7 LM3647 Reference Design Demonstration Board The demo board provides a combined multi chemistry solution with hardw
8. 2013 Texas Instruments Incorporated la TEXAS INSTRUMENTS www ti com Application information 6 Application information 6 1 Typical Example 6 1 1 Ni Cd Ni MH 5V FOV Te IC2 10 100 nF 22 nF Vout Yin gt SEL4 Z GND GND 6 c7 NC NCES m eee oa LM78L05S0 5V 5V eu mia athe f R18 ao no ee gg ae BUZZER l Q3 R1 i R16 f R17 doa 330 330 330 a 2 8 2 pF IC1 5V D6 D4 D3 7 Nie odin a Fi gt DISCHARGE a ep TEMPERATURE OOO es os a 7 om CON SIP 2P TEMPERATURE R6 1 5K CON SIP 2P 5V R15 l 1k S G DISCHARGE _ gt r cy r A Figure 7 Ni Cd Ni MH Set To SEL1 SEL2 SEL3 Vec No Discharge before Charge Ni MH Fast PWM LM3647 has current feedback Hi Z Discharge before Charge NA NA GND Maintenance Charge Only Ni Cd Slow PWM external current control SNVA023B September 2000 Revised May 2013 AN 1164 LM3647 Reference Design Demonstration Board 9 Submit Documentation Feedback Copyright 2000 2013 Texas Instruments Incorporated I TEXAS INSTRUMENTS Application information www ti com 6 2 Li lon 5V 5V UNREGULATED_DC MAX20V t C1 TIP 121 D1 10 100nF 22nF C L SEL4 R23 1 uF 100k Q3 5V lt SEL4 SEL3 T 8 2 pF 1 D7 D4 D3 R9 2 ee ET nee 0 047 MAX20V 2 a 3 DiscHG LS H DISCHARGE vets O LEDI TEMPI TEMPERATURE R19 PF tt fi ae w t e TE Vere cea lt 10
9. B Jumper J14 Used to Select Different Amplification Levels of the PWM Signal The jumper J10 is used to select between different current sense resistors The values mounted are 0 047Q and 0 1000 Q Q 1 0 047 Cc Figure 11 Jumper J10 Used to Select Between Different Current Sense Resistors SNVA023B September 2000 Revised May 2013 AN 1164 LM3647 Reference Design Demonstration Board 11 Submit Documentation Feedback Copyright 2000 2013 Texas Instruments Incorporated I TEXAS INSTRUMENTS LM3647 Reference Design Demonstration Board www ti com The different current sense voltage amplification level is selected via CURRENT jumpers J9 and J13 both jumpers must be changed in pairs see Figure 12 The upper values correspond to a current sense resistor of 0 047Q while the lower correspond to 0 1000 see Figure 11 1600 750 mA 1200 560 mA 1000 470 mA 830 390 mA 1600 750 mA 1200 560 mA 1000 470 mA 830 390 mA d3 J15 Figure 12 CURRENT Jumpers J9 and J13 The battery voltage is selected with the Voltage jumpers J11 and J12 see Figure 13 for settings Ni 4 Cells Ni 4 Cells Ni 8 Cells Ni 8 Cells Ni 6 Cells Ni 6 Cells Li 4 Cells Ni 10 Cells Li 4 Cells Ni 10 Cells Li 3 Cells Li 3 Cells Li 2 Cells Ni 5 Cells Li 2 1 Cells Ni 5 Cells Li 1 Cells J11 J12 Figure 13 Voltage Jumpers 11 and 12 The jumper J3 is used to connect to an optional NTC resistor If no temperature sensor is used the jumper J8 must be
10. are for both external constant current source and LM3647 controlled charge current Located near the top left corner of the board is the power supply connector next to the heatsink When using the external constant current source a power resistor needs to be connected at the connector marked 31 7 resistor The values of the resistor can be calculated using the Equation 4 mentioned earlier At the bottom right corner of the board are two connectors that lead to the battery and discharge resistor The value of the discharge resistor depends on the battery pack voltage and the maximum discharge rate The demo board has different jumpers that are assigned to different setups Some of the components are not populated providing support for user specific values The timeout jumper J18 is used to select different timeouts from 2 4C to 0 4C The values mounted on the demo board result in timeouts corresponding to the charge rates shown in Figure 9 O O O O LO w N SS O O AN J18 Figure 9 Timeout Jumper J18 Used to Select Different Timeouts From 2 4C to 0 4C The PWM jumper J7 is used to connect the PWM signal to either the external constant current source marked slow or the RC filter that is connected to the operational amplifier marked fast The PWM FB jumper J14 is used to select different amplification levels of the PWM signal The jumper with the battery voltage ranges are shown below J14 2 4 9V 4 5 9V J 15 18V Figure 10 PWM F
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12. baal 0 75 x 0 C gt R 100k0 C 47nF 800 mAh The actual timeouts with RCIN 2 5 MHz is Phase Timeout Fast Charge 330 Minutes Topping Charge 80 Minutes EXAMPLE 2 Lilon Battery Pack Capacity 1200 mAh Charge Current 1500 mA 1500 mA Charge Rate 1 25 x 1 20 R 100k0 C 22nF 1200 mAh The actual timeouts with RCIN 2 5 MHz is Phase Timeout Fast Charge Constant Current 130 Minutes Topping Charge Constant Voltage 190 Minutes 5 2 6 Setting The Charge Current The charge current is selected by setting the current sensing resistor and the gain of the differential amplification stage The current sensing resistor R5 should be dimensioned such that the voltage drop over it is not too small since the signal will be more susceptible to noise and offsets in the amplification stage The resistance should not be too large either especially in high current applications because this will only generate more heat from the component A suitable value is one where 50 mV dropped across the resistor when maximum current flows through it The differential signal is then amplified inverted and centered around the 2 5V reference by the operational amplifier and fed to the CS pin on the LM3647 The gain must be dimensioned by setting the appropriate ratio between R1 R2 and R3 R4 Figure 4 is dimensioned for a maximum current of about 1 1A This was dimensioned using the following formula Max Current READ X
13. ck circuitry The high speed PWM is filtered to a DC level and fed into an operational amplifier that controls a power NPN transistor The LM3467 requires charge current feedback to control the charge current Modes of Operation Charging Ni Cd Ni MH Batteries The charger detects that a battery is connected when the CEL pin gt 1 0V The charger can also detect a battery that has been deeply discharged and does not have any voltage across the battery terminals This is accomplished by applying a small pre charge current once every minute for up to 15 seconds The deeply discharged battery will accept this charge and the battery potential will eventually rise above the 1 0V limit to initiate normal charging When the charger has detected a battery CEL pin gt 1 0V it checks to see if the temperature is within range to start charging If it is then it applies a small current of 0 2C for approximately 5 minutes If the battery voltage exceeds the maximum battery voltage CEL pin gt 3 017V the LM3647 stops charging and stays in error mode until the battery is removed If the battery voltage has not risen above the bad battery threshold CEL pin lt 1 2V then the battery is considered to be defective and the charger goes into error mode If the battery passes all tests then after the five minutes have passed the charger starts the next phase Fast Charge During Fast Charge the charger applies a constant current to the battery and monito
14. d maximum time e Dynamically detects battery insertion removal short circuit and bad battery without additional hardware e Supports charging of battery packs with 2 8 cells of Ni Cd Ni MH or 1 4 cells of Li lon e Three LED indicators and one Buzzer output indicate operational modes e Ni MH Ni Cd charge mode Li lon charge mode or discharge mode can be selected manually e PWM switching controller SNVA023B September 2000 Revised May 2013 AN 1164 LM3647 Reference Design Demonstration Board 1 Submit Documentation Feedback Copyright 2000 2013 Texas Instruments Incorporated I TEXAS INSTRUMENTS Documentation Information www ti com 3 4 1 4 2 4 3 4 4 J Type Select Ni MH Ni Cd Hi Z Li lon Q lt Z amp J a Ol 2 Charge Mode No discharge N Maintenance charge only Hi Z Discharge before charge 9 lt O J i 2 Maintenance Mode Charge indefinitely i O N No charge and restart fast charge if battery becomes discharged Hi Z Charge indefinitely and restart fast charge if battery becomes discharged J5 J6 Regulation Method Cell Voltage Voc Voc Fast LM3647 controls charge current GND Slow External LM317 charge control GND Voc Fast LM3647 controls charge current GND Slow External LM317 charge control Hi Z Voc Fast 4 2V Cell Li lon GND Fast 4 1V Cell Li lon Timeout Timeout settings J18 set according to charge rate C Temperature Input The optional Temperature
15. e The transistor Q2 must be able to handle the maximum discharge current e The Diode D1 must be able to handle the maximum charge current Clarifications Regarding Circuit Schematics The circuitry with Q4 R26 and R27 is used to protect the battery from excessive charge current When the current flows through the current sense resistor R9 and is amplified by U2 the voltage at U2 s output drops from 2 5V until Q4 starts conducting It discharges the RC network that generates the DC voltage from the PWM output of the LM3647 Setting The Charge Timeout The LM3647 uses the charge timeout value as a backup termination method if the normal termination methods fail The charge timeout also controls the length of some of the phases like the Topping Charge phase Ni Cd Ni MH The timeout is selectable from a charge rate of 3 2C to 0 4C Table 1 shows which values will result in a certain timeout Table 1 Charge Timeouts ne AE tency soporte minutes 100 25 70 100 2 4C 160 40 110 160 1 4C 190 50 130 190 1 26 260 65 170 260 0 9C 330 80 220 330 0 7C 450 115 300 450 0 5C 540 135 360 540 0 4C SNVA023B September 2000 Revised May 2013 Submit Documentation Feedback Copyright 2000 2013 Texas Instruments Incorporated AN 1164 LM3647 Reference Design Demonstration Board 5 I TEXAS INSTRUMENTS Functional Description www ti com EXAMPLE 1 NiMH Battery Pack Capacity 800 mAh Charge Current 600 mA Charge Rate
16. ed and the charger can behave in different modes depending on SEL1 It can either maintenance charge the battery and restart the charge process if the battery voltage drops below the maintenance restart threshold value CEL lt 2 153V or just maintenance charge the battery and don t restart the charge process if the battery becomes discharged The last mode is no maintenance charge and restarts the charge process if the battery voltage drops below the maintenance restart threshold value CEL lt 2 158V Components Critical to Total Charger Performance e The capacitance C2 connected to CEXT must be of a type that has low internal resistance low loss high stability and low dielectric absorption The capacitance mounted on the demo board is a metallized polyester type from WIMA 2220 series e The operational amplifiers U1 and U2 must be capable of rail to rail output and have a high PSRR Power Supply Rejection Ratio because they are both powered directly from the unregulated DC input U1 must also have enough current drive to control the transistor Q3 U2 should preferably have a low input offset since this error will be amplified e The regulator IC2 criteria is that it has to be able to handle the input DC voltage and deliver enough current to drive the circuitry all LED s buzzer LM3647 e The transistor Q3 must be able to handle the charge current and depending on charge current must be provided with an adequate heatsink
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18. ks to see if the temperature is within range to start charging If it is then it applies a small current of 0 2C for approximately 1 minute If the battery voltage is close to fully charged the charger will not reach the charging voltage within 1 minute and the charge process will restart This occurs only with batteries that are already fully charged and consequently should not be recharged If the battery voltage has not reached the Li lon battery qualification voltage CEL pin gt 1 2V within 1 minute of the Qualification Phase the battery is considered to be defective and the charger goes into error mode It stays there until the battery is removed CEL pin lt 1 0V AN 1164 LM3647 Reference Design Demonstration Board SNVA023B September 2000 Revised May 2013 Submit Documentation Feedback Copyright 2000 2013 Texas Instruments Incorporated la TEXAS INSTRUMENTS www ti com 5 2 3 5 2 4 5 2 5 Functional Description The next phase is Fast Charge Constant Current During this phase the current is constant and the battery voltage will slowly rise due to the charging When the battery has reached its maximum battery voltage CEL at 2 675V or 2 74V depending on SEL3 it will go to the next phase which is Fast Charge Constant Voltage During this phase the charger will keep the voltage constant and stay in this phase until the current has decreased to a threshold value CS at 2 3V The battery is now fully charg
19. l TEXAS INSTRUMENTS AN 1164 LM3647 Reference Design Demonstration Board User s Guide SNVA023B September 2000 Revised May 2013 1 General Description The LM3647 is a charge controller for Nickel Cadmium Ni Cd Nickel Metal Hydride Ni MH or Lithium lon Li lon batteries The device uses a pulsed current charging or a constant current charging technique The device can also be configured to discharge before charging Throughout the charging sequence the LM3647 monitors voltage and or temperature and time in order to terminate charging e Negative delta voltage AV e Maximum voltage e Optional Delta temperature delta time AT At e Optional Maximum temperature e Backup Maximum time The LM3647 is user configurable for three battery chemistries Ni Cd Ni MH or Li lon In Ni Cd Ni MH mode four different charging phases are used e Softstart charge e Fast charge e Topping charge e Maintenance charge In Li lon mode four different charging stages are used e Qualification e Fast Charge Phase 1 Constant Current e Fast Charge phase 2 Constant Voltage e Maintenance charge 2 Key Features e Auto adaptive fast charge e High resolution accurate voltage monitoring prevents Li lon under charge or overcharge e Fast charge pre charge and maintenance currents are provided Different currents are selectable via external resistors e Fast charge termination by temperature time maximum voltage maximum temperature an
20. r network The recommended tolerance of the resistors are 0 1 but 1 may be used with a marginal loss of battery capacity by subtracting the tolerance of the divider network from the maximum battery voltage e Using the LM3647 without current feedback for Ni Cd Ni MH only slow PWM mode This mode uses an external constant current power source which is switched on and off according to the charge phase of the LM3647 The frequency is approximately 0 1 Hz The advantage of this charge method is that operational amplifiers and the current feedback circuitry are not needed which provides a low cost solution The dimensioning of the voltage divider network is performed the same way The constant current source is dimensioned in the following manner 1 25 V4 loUT Ry Vy Voltage drop across D1 7 UNREGULATED_DC 2 V_OUT SLOW_PWM L_ Figure 6 LM3647 Regulator The LM3647 regulates the constant current source by turning the transistor Q1 on and of see Figure 6 When the transistor is off the LM317T regulator feeds a constant current to the battery at V_OUT When the transistor is on the output from the LM317 is limited to 1 25V which should be greater than the battery voltage Charge Phase Duty Cycle Soft Start 10 Fast Charge 100 Topping Charge 10 Maintenance Charge 5 8 AN 1164 LM3647 Reference Design Demonstration Board SNVA023B September 2000 Revised May 2013 Submit Documentation Feedback Copyright 2000
21. rs both battery voltage and temperature The charger is looking for a drop in the battery voltage that normally occurs at the end of the Fast Charge cycle The size of the voltage drop differs depending on battery type Ni Cd Ni MH For Ni Cd it is approximately 50 mV cell and for Ni MH it is approximately 17 mV cell If the temperature rise is larger than 50 mV minute 1 C minute when charging Ni MH batteries the battery has reached the end of the Fast Charge cycle During charging the temperature input is constantly measured to ensure that the battery s temperature is within proper range If the temperature is out of range the charger aborts the charge and goes into error mode During the next charge phase Topping Charge the LM3647 applies a small current of 0 2C for a time set by the time selection RC network This phase may be followed by a Maintenance Charge phase depending on selection pins Charging Li lon Batteries The charger detects that a battery is connected when the CEL pin gt 1 0V The charger can also detect a battery that has been deeply discharged and does not have any voltage across the battery terminals This is accomplished by applying a small pre charge current once every minute for up to 15 seconds The deeply discharged battery will accept this charge and the battery potential will eventually rise above the 1 0V limit to initiate normal charging When the charger has detected a battery CEL pin gt 1 0V it chec
22. shorted see Figure 14 The demo board was designed for an NTC thermistor from Siemens B57861S302F40 with the following specifications 3KQ 25 C B 3988 If an NTC with different characteristics is used then the resistor R28 may need to be changed The charger uses voltage levels to trigger under over temperature conditions The voltage at the temperature input must be between 2 2V or 0 5V for the charger to start During charging the voltage must stay between 3 0V for Li lon or 3 15V for Ni Cd Ni MH and 0 5V or the charger will register a temperature fault and abort the charge TaM JS J8 Figure 14 Jumper J3 or Jumper 8 SNVA023B September 2000 Revised May 2013 12 AN 1164 LM3647 Reference Design Demonstration Board Submit Documentation Feedback Copyright 2000 2013 Texas Instruments Incorporated 13 TEXAS INSTRUMENTS www ti com LM3647 Reference Design Demonstration Board Voltage at Temperature input Temperature in C Figure 15 Voltage Temperature The three jumpers J2 J5 and J6 are connected to the three selection pins SEL1 SEL2 and SEL3 These jumpers are used to select how the charger should behave see Table 1 431 resistor B Bl BF U lt l 74 vu i Timeout Bocca ii 3 O000O E O Buzzer IC 1 O0O00000 HFHOOOO00 Battery Current OOOODWY IOO00OM 13 OOO000 O00000 J15 Discharge resistor m 4Q Figure 16 Jumpers J2 J5 and J6 Connected to
23. tors The values available are 0 0470 and 0 1000 see Figure 2 000 0 0470 Cc Figure 2 Jumper J10 Selects Between Current Sense Resistors The charge current is set with jumpers J9 and J13 Figure 3 shows two possible currents that depend on how jumper J10 is set The higher current is selected when J10 is set to 0 047Q and the lower current is selected when J10 is set to 0 100Q A A A 1600 750m 1200 560m 1000 470 m 830 390 mA 1600 750 mA 1200 560 mA 1000 470 mA 830 390 mA J9 TE Figure 3 Charge Current is Set with Jumpers J9 and J13 SNVA023B September 2000 Revised May 2013 AN 1164 LM3647 Reference Design Demonstration Board 3 Submit Documentation Feedback Copyright 2000 2013 Texas Instruments Incorporated I TEXAS INSTRUMENTS Functional Description www ti com 5 5 1 5 2 5 2 1 5 2 2 Functional Description General The LM3647 has voltage and current sensing inputs that are used to control a PWM output The voltage input is connected to the battery via a resistor divider network and the current input is connected to an operational amplifier that amplifies the voltage across a current sense resistor located at the positive battery terminal The PWM output can be configured as a high speed PWM or as a low speed ON OFF output for an external current regulator The latter is for low cost Ni Cd Ni MH charger applications eliminating the need for any operational amplifiers or current feedba
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