Application Note 1164 LM3647 Reference Design User`s Manual
Contents
1. 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 dis charge mode can be selected manually e PWM switching controller DOCUMENTATION INFORMATION The following documentation describes how to use the LM3647 demo board and also gives a few tips on design calculations Please note that not all components on the demo board are used when designing a charger appli 2000 National Semiconductor Corporation AN101315 National Semiconductor Application Note 1164 September 2000 cation The demo board has extra components to make it simple for the user to try out different batteries and configu rations There are actually two different charge current regu lation methods and these are referred to as fast and slow LM317 JUMPER SETTINGS Charge indefinitely becomes discharged Hi Z Charge indifinitely and restart fast charge if battery becomes discharged Fast Slow Fast Slow Fast Fast Regulation Method Cell Voltage LM3647 controls charge current External LM317 charge control LM3647 controls charge current External LM317 charge control 4 2V Cell Li lon 4 1V Cell Li lon Hi Z Voc GND Timeout Timeout settings J18 set according to charge rate C See Section 3 0 for more information Temperatur2. have any voltage across the battery terminals This is accomplished by apply ing 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 min utes 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 monitors both battery voltage and tem perature 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 s approximately 50 mV cell and for Ni MH it s approximately 17 mV cell If the temperature rise is larger than 50 mV minute 1 C minute when charging Ni M
3. of a type that has low internal resistance low loss high sta bility 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 PowerSup plyRejectionRatio because they are both powered di rectly 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 pro vided with an adequate heatsink 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 1 2 2 2 Clarifications Regarding Circuit Schematics The circuitry with Q4 R26 and R27 see section below 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 1 2 2 3 Setting The Charge T
4. 101315 14 The jumper J3 is used to connect to an optional NTC resistor If no temperature sensor is used the jumper J8 must be shorted 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 be tween 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 COTA Eno wre J3 J8 AN101315 15 m e a N Oo a n Voltage at Temperature input 10 5 0 5 10 15 20 25 30 35 40 45 50 Temperature in C AN101315 16 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 Charger Modes table 317 resistor g Timeout Boog TT Buzzer O O00000 Mz OO00O lt O oo0oo0oo0o000 aoo0oo0o00o0 Battery N D6 D4 D3 jenuey sasn UbIseg 29u3134 3Y ZYVIENWNT LM3647 l Current COOOMY lIOOCOn Ji O0O000 O0O000 C2 Discharge resistor E AN101315 17 LIFE SUPPORT POLICY NATIONAL S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SU
5. H batteries the battery has reached the end of the Fast Charge cycle During charging the temperature input is constantly mea sured 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 see section below This phase may be followed by a Maintenance Charge phase depend ing on selection pins 1 2 2 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 apply ing 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 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
6. LM3647 Reference Design User s Manual 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 chemis tries 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 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 and maximum time e Dynamically detects battery insertion removal short cir cuit and bad
7. PPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION As used herein 1 Life support devices or systems are devices or 2 A critical component is any component of a life systems which a are intended for surgical implant support device or system whose failure to perform into the body or b support or sustain life and can be reasonably expected to cause the failure of whose failure to perform when properly used in the life support device or system or to affect its accordance with instructions for use provided in the safety or effectiveness labeling can be reasonably expected to result in a significant injury to the user National Semiconductor National Semiconductor National Semiconductor National Semiconductor Corporation Europe Asia Pacific Customer Japan Ltd D Americas Fax 49 0 180 530 85 86 Response Group Tel 81 3 5639 7560 Tel 1 800 272 9959 Email europe support nsc com Tel 65 2544466 Fax 81 3 5639 7507 z Fax 1 800 737 7018 Deutsch Tel 49 0 69 9508 6208 Fax 65 2504466 A Email support nsc com English Tel 44 0 870 24 0 2171 Email ap support nsc com l www national com Fran ais Tel 33 0 1 41 91 8790 Ja National does not assume any responsibility for use of any circuitry described no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications
8. Voltage Cell 1 2V NumberOfCells 5 Battery PackVoltage 1 2x5 6V www national com MaximumBattery Voltage Cell 1 85V MaximumBattery Voltage 1 85x5 9 25V When the Maximum Battery Voltage has been determined the voltage divider network has to be dimensioned using the following formula R7 o an MaximumBatteryVoltage x R6 R7 CEL 3 071V AN101315 3 BATTERY _ VOLTAGE R6 CEL R7 C1 AN101315 4 e For Li lon 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 bat tery may become damaged Never exceed the recom mended maximum voltage or current for a Li lon bat tery The dimensioning is done in the following manner First calculate the maximum battery voltage for the specific battery pack See example below BatteryVoltage Cell 3 6V NumberOfCells 2 Battery PackVoltage 3 6x2 7 2V MaximumBatteryVoltage Cell 4 1V MaximumBattery Voltage 4 1x2 8 2V When the maximum battery voltage has been determined the voltage divider network has to be dimensioned using the following formula f R7 MaximumBatteryVoltage x R6 R7 The LM3647 has two different regulation voltages which the user can select These are 2 675V SEL3 tied to GND and 2 740V SEL3 tied to Vgc This selection pin can be used to configure the charger to regulate for different input vol
9. 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 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 charged and the charger can be have in different modes depending on SEL1 It can either maintenance charge the battery and restart the charge pro cess 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 mainte nance charge and restarts the charge process if the battery voltage drops below the maintenance restart threshold value CEL lt 2 153V 1 2 2 1 Components Critical to Total Charger Performance e The capacitance C2 connected to CEXT must be
10. e Input The optional Temperature 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 l e JZ slow defines maximum voltage output See also Section 3 0 LM3647 REFERENCE DE SIGN DEMO BOARD Voltage Measurement The battery voltage is selected with the Voltage jumpers J11 amp J12 depending on number of cells chemistry 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 www national com jenuey sasn UbIseg 29U3134 34 J POINT VOLL NV AN 1164 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 AN101315 14 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 LM3647 Current Regulation The jumper J10 is used to select between different current sense resistors The values available are 0 047Q and 0 100Q 0 1000 0 0470 J10 m ee AN101315 12 Th
11. e charge current is set with jumpers J9 and J13 The figure 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 0 100 600 750 mA 200 560 mA 1000 470 mA 830 390 mA 1600 750 mA 1200 560 mA 1000 470 mA 830 390 mA 1 1 J13 eeeee 1 0 FUNCTIONAL DESCRIPTION AN101315 13 1 1 General The LM3647 has voltage and current sensing inputs that are used to control a PWM output The voltage input is con nected 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 feedback 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 www national com 1 2 Modes of Operation 1 2 1 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
12. ery voltage NA 4 1V Cell drops 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 differnet 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 is used then minor adjustments have to be done to the voltage measurement resistor divider 7 www national com VOLL NV AN 1164 3 0 LM3647 REFERENCE DESIGN DEMO BOARD The demo board provides a combined multi chemistry solu tion with hardware 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 317 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 dif ferent 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 diffe
13. imeout 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 The table below shows which values will result in a certain tim eout TABLE 1 Charge Timeouts Ni Cd Ni MH Li lon CV Appropriate minutes Charge Rates R Value C Value Fast Charge En ana PA minutes EXAMPLE 1 NiMH Battery Pack Capacity 800 mAh Charge Current 600 mA 600 mA Charge Rate 800 mAh The actual timeouts with RCIN 2 5 MHz is 0 75 x 0 7 gt R 100kQ C 47nF AN101315 18 Phase Timeo 330 Minutes Fast Charge Topping Charge EXAMPLE 2 80 Minutes www national com VOLL NV AN 1164 Lilon Battery Pack Capacity 1200 mAh Charge Current 1500 mA 1500 mA Charge Rate 1200 mAh The actual timeouts with RCIN 2 5 MHz is Phase O m 1 25 1 2C gt R 100k0 C 22nF AN101315 19 Fast Charge Constant Current 130 Minutes Topping Charge Constant Voltage 190 Minutes 1 2 2 4 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 i
14. pping Charge 10 Maintenance Charge 5 2 675V 2 740V if SEL3 is set to Voc www national com VOLL NV AN 1164 2 0 APPLICATION INFORMATION 2 1 Typical Example 2 1 1 Ni Cd Ni MH 5V te 10 100 nF 22 nF 5V D1 IN gt SEL4 c5 c6 222 R4 10k LM78L05S0 at G S SEL3 SEL4 GND 5V Z TEMPERATURE RS SK CON SIP 2P TEMPERATURE R6 1 5K CON SIP 2P G DISCHARGE gt A AN101315 8 Ve No CAA before Charge Fast PWM LM3647 has current feedback Discharge before Charge ma oo pa a Maintenance Charge Only Slow PWM external current control www national com 6 2 1 2 Li lon 5V 5V UNREGULATED_DC MAX20V Tee 10 100 nF 22 nF gt SEL4 6 R23 ye 100 pF 100k LM78L05S0 TIP121 D1 Q3 5V 5V 5V BUZZER SEL4 SEL3 8 2 pF i i SEL3 D7 D4 D3 3 SEL4 R9 X o X RCIN se eS 0 047 GND MAX20V 2 NX N Ne 5V 2 cc RESET DISCHARGE a TEMPERATURE R19 LE r ae Ce 10 CONRA 2P R21 CONRA 2P eu Fa 15k D2 R2 K 68k i he BAS16LT1 NC 10 uF TEMPERATURE C i gt 2 5Vper DISCHARGE L gt R3 R28 a NC DS 100k w LM4040A 2 5 A AN101315 9 SEL1 After charging maintenance charging until battery removal 4 2V Cell After charging maintenance charging until battery removal If battery Li lon NA voltage drops below a predefined value the charger restarts the charge process GND After charging no maintenance charging is applied If batt
15. rent timeouts from 2 4C to 0 4C The values mounted on the demo board result in timeouts corresponding to the charge rates shown below AN101315 10 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 amplifi cation levels of the PWM signal The jumper with the battery voltage ranges are shown below J14 2 4 5V 4 5 9V 9 13V 13 18V AN101315 11 The jumper J10 is used to select between different current sense resistors The values mounted are 0 047Q and 0 100Q J10 me e AN101315 12 0 1000 0470 0 The different current sense voltage amplification level is selected via CURRENT jumpers J9 and J13 both jumpers must be changed in pairs see figure below www national com The upper values correspond to a current sense resistor of 0 047Q while the lower correspond to 0 100Q see previous figure 1600 750 mA 1200 560 mA 1000 470 mA 830 390 mA 1600 750 mA 1200 560 mA 1000 470 mA 830 390 mA J13 qe oO AN101315 13 The battery voltage is selected with the Voltage jumpers J11 and J12 see below 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 AN
16. t 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 refer ence 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 R3 and R2 R4 The figure below is dimensioned for a maximum current of about 1 1A This was dimensioned using the following formula R2 R1 R5 R1 R3 R2 R4 R2 5 1kQ R1 100kQ R5 0 047kn Max Current 1 09Ampere Max Current 2 5V REFERENCE POWERSUPPLY AN101315 2 1 2 2 5 Setting Maximum Battery Voltage The resistor network see the figure below scales the bat tery 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 toler ances 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 example below Battery
17. tages 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 resistor 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 amplifi ers and the current feedback circuitry are not needed which provides a low cost solution The dimensioning of the volt age divider network is performed the same way The con stant current source is dimensioned in the following manner 125 9 lout a Vy Voltage drop across D1 UNREGULATED_DC L gt V_OUT SLOW_PWM L_ AN101315 7 The LM3647 regulates the constant current source by turn ing the transistor Q1 on and off 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 0 Fast Charge 100 0 To
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