Cypress Semiconductor CY8C24794 manual

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  • Page 1

    Power Management - L ow - Cost, Two-Cell Li -Ion/Li-Pol Battery Charge r with Cell-Balancing Support November 25, 2007 Document No. 001- 17394 Rev. * B - 1 - AN2309 Author : Oleksandr Karpin Associated Project : Yes Associated Part Family : CY8C 24x23A, CY8C24794, CY8C27x4 3, CY8C29x66 T GET FREE SAMPLES HERE T H Software Version : PSoC Designer ?[...]

  • Page 2

    AN2309 November 25, 2007 Document No. 001- 17394 Rev. * B - 2 - Table 1. Specifications for Two-Cell Li-Ion/Li-Pol Battery Charger with Cell-Balancing Support Item Item Value Battery Charger Parameters Built-In Battery Charger Type Two-cell Li- Ion/Li -Pol batter y charger Power Supply Voltage 10…14V Power Consumption 35 mA Battery Current Measur[...]

  • Page 3

    AN2309 November 25, 2007 Document No. 001- 17394 Rev. * B - 3 -  Temperature gradient across the battery pack. Temperature mismatches of 15 degrees Celsius can cause up to 5- percent capacity differential among cells. Such a temperature gradient is relatively common in densely packed products, where multiple heat sources are located close to the[...]

  • Page 4

    AN2309 November 25, 2007 Document No. 001- 17394 Rev. * B - 4 -  Cell Balancing Time : If C is the cell capacity and b V is the battery voltage, and the requirement is to eliminate the amount of imbalance (in percent) in o ne hour of balancing time, then the power dissipation on balancin g circuit P bal is : 100% b CV P bal Equation 10 For examp[...]

  • Page 5

    AN2309 November 25, 2007 Document No. 001- 17394 Rev. * B - 5 - A two-cell battery charger structure with cell -balancing support is shown in Figure 3 . Similar battery charger structures are explained in detail in AN225 8 , AN2294 , and AN2267 . Note that the fuel gauge function can easily be added to this project without changing any hardware: It[...]

  • Page 6

    AN2309 November 25, 2007 Document No. 001- 17394 Rev. * B - 6 - Device Schematic The schematics shown in Figure 4 on page 7 and Figure 5 on page 8 constitute a complete two-cell battery charger. A signal from the PWM goes to the RC-filter, which co nsists of resistor R4 and capacitor C4. A constant voltage signal proportional to the PWM duty cycle [...]

  • Page 7

    AN2309 November 25, 2007 Document No. 001- 17394 Rev. * B - 7 - Figure 4. Two-Cell Battery Charger Schematic – CPU, Cell Balancing, and Measuring Equipment BAL2 Q1 IR LML6402 BAL1 CALIBRATION DR I VE 1 2 3 4 5 J2 ISSP/ D EBU G X R ES VCC TX TP1 BAL1 Vref P0[7] 1 P0[5] 2 P0[3] 3 P0[1] 4 P2[7] 5 P2[5] 6 P2[3] 7 P2[1] 8 SMP 9 P1[7] 10 P1[5] 11 P1[3][...]

  • Page 8

    AN2309 November 25, 2007 Document No. 001- 17394 Rev. * B - 8 - Figure 5. Two-Cell Battery Charger Schematic – Power Supply and User Interface R 30 33 1 2 J4 POW ER 12V D C PSoC C 12 0. 33u 16V IN 1 OU T 3 U2 L78L05/TO D6 BAT 54C Close to PSoC C 15 0. 1u D8 BAS16 VC C R 29 1K VC C Vbias POW ER - + C9 100u 16V C 10 0. 1u 16V + POW ER + SW 1 POW ER[...]

  • Page 9

    AN2309 November 25, 2007 Document No. 001- 17394 Rev. * B - 9 - Figure 6. PSoC Internal User Module Configuration Battery Measurement To provide a correct implementation of the charge and cell - balancing algorithms, the charge current, batter y voltage and temperature must be measured accurately. These three parameters are measured as the voltage [...]

  • Page 10

    AN2309 November 25, 2007 Document No. 001- 17394 Rev. * B - 10 - The voltage measurement also is performed by the INA on the corresponding resistor. The resistive dividers (R7, R6), (R13, R12), and (R18, R19) transform cell voltage into signals suitable for the PSoC device. It is ver y important to use the high precision resistors in the resistive [...]

  • Page 11

    AN2309 November 25, 2007 Document No. 001- 17394 Rev. * B - 11 - Figure 7. Temperature Profile T HOT_STOP T HOT_RESTART T COLD_STOP T COLD_RESTART T BATT Charge in process Charge in Process No Charge T DISCH_COLD_STOP T DISCH_HOT_STOP No Discharge No Discharge Two-Cell Battery Charger Fir mware The two-cell battery charger firmware is separated int[...]

  • Page 12

    AN2309 November 25, 2007 Document No. 001- 17394 Rev. * B - 12 - Figure 8. Two-Cell Battery Charger State Diagram Activation Initialization Rapid Error Charge Complete Wait For Temperature Full Discharge Discharge 1 7 4 5 8 3 2 12 11 9 10 6 13 Initially the charger is in the In itialization state. After some device prepar ation, the charger goes to[...]

  • Page 13

    AN2309 November 25, 2007 Document No. 001- 17394 Rev. * B - 13 - Figure 9. Two-Cell Battery Charger Firmware Flowchart Part 1 Start Init Device Measure V b1 , V b2 , I ch , T b Calc V bmin , V bmax State Activation Set I reg =I ACT ; Regulate State Initialization Yes Set Activation State Charge On Start t ACT , t CH , Timing Open LOAD Out Yes No Ch[...]

  • Page 14

    AN2309 November 25, 2007 Document No. 001- 17394 Rev. * B - 14 - Figure 10 . Two-Cell Battery Charger Firmware Flowchart Part 2 State Charge Complete Charge Off Timers Off Yes No State Error Yes Charge Off Timers Off Check Charge Restart Condition Set Initialization State Yes No State Wait For Temperature Charge Off Timers Off Yes No True Yes No St[...]

  • Page 15

    AN2309 November 25, 2007 Document No. 001- 17394 Rev. * B - 15 - The minimum cell-balance parameter consists of the voltage measure error value plus the internal impedance error value. The cell-balancing algorithm that is implemented here does not significantly lengthen the charge time. The c harger monitors all of the cell voltages. Cell balancing[...]

  • Page 16

    AN2309 November 25, 2007 Document No. 001- 17394 Rev. * B - 16 - Two-Cell Battery Charger Par ameters All two-cell battery charger parameters are located in the header file globdefs.h in th e project folder. The header file globdefs.h contains the following parameters: Table 2. Two-Cell Battery Charger Parameters Parameter Unit Description Charging[...]

  • Page 17

    AN2309 November 25, 2007 Document No. 001- 17394 Rev. * B - 17 - Cell-Balancing Paramet ers All cell-balanci ng parameters are located in the header file globdefs.h in the project folder. T he header file globdefs.h contains the following parameters: Table 3. Cell-Balancing Parameters Parameter Unit Description Vmeas_err V Resistor Matrix Error for[...]

  • Page 18

    AN2309 November 25, 2007 Document No. 001- 17394 Rev. * B - 18 - Appendix Charge/Discharge and Cell -Balancing Profile Examples Figure 13 . Charge/Discharge Manager Profile Constant Current Charge Constant Voltage Charge Battery Discharge Cell Voltages Without Charge Interrupt Charger State Cell-Balancing State Charge /Discharge Current Thermistor [...]

  • Page 19

    AN2309 November 25, 2007 Document No. 001- 17394 Rev. * B - 19 - Figure 14 . Cell-Balancing Activity Profile Voltage Imbalance Value Cell Voltages With Charge Interrupt [+] Feedback[...]

  • Page 20

    AN2309 November 25, 2007 Document No. 001- 17394 Rev. * B - 20 - Figure 15 . Cell-Balancing Parameter Profile Screen About the Author Name: Oleksandr Karpin Title: Application Engineer Background: Oleksandr received a PhD ’s degree in com puter science in 2008 from Lviv Polytechnic National Universit y (Ukraine). His intere sts include embedded s[...]

  • Page 21

    AN2309 November 25, 2007 Document No. 001- 17394 Rev. * B - 21 - Document History Document Title: Power Management - Low-Cost, Two-Cell Li-Ion/Li-Pol Battery Charger with Cell-Balancing Support Document Number: 001-17394 Rev. ECN Orig. of Change Submission Date Description of change ** 1352043 HMT 08/29/2007 Obtain spec. # for note to be added to s[...]