SLUAAQ5 May   2024 BQ769142 , BQ76942 , BQ76952 , BQ76972

 

  1.   1
  2.   Abstract
    1.     Trademarks
  3. 1 General Operation FAQs
    1. 1.1  What are the differences between the devices in the BQ769x2 family?
    2. 1.2  What are the differences between the BQ769x0 and BQ769x2 device families?
    3. 1.3  Do I need a microcontroller to control the device or can the device run autonomously?
    4. 1.4  What is the minimum number of cells required to operate the device and how to connect them?
    5. 1.5  Can the device perform gauging to calculate State of Health (SOH) and State of Charge (SOC)?
    6. 1.6  How does unused pins needs to be connected?
    7. 1.7  What does support random cell attachment means?
    8. 1.8  How do I RESET the BQ769x2 device?
    9. 1.9  How does the BQ769x2 recover from a fault?
    10. 1.10 Does the BQ769x2 support open wire detection?
  4. 2 Control FETs FAQs
    1. 2.1  What are the tradeoffs of High side vs Low side gate driving?
    2. 2.2  Can the BQ769x2 be used for low-side FET driving?
    3. 2.3  Is the CP1 capacitor necessary for low-side switching?
    4. 2.4  How long does the BQ769x2 take to turn on the FETs on power up?
    5. 2.5  What are the typical voltages for the Charge (CHG) and Discharge (DSG) pins?
    6. 2.6  What are the voltage ranges of the Precharge (PCHG) and Predischarge (PDSG) pins?
    7. 2.7  How can I achieve faster gate turn-offs for DSG?
    8. 2.8  Why are the FETs turning OFF while data memory registers are being configured in CONFIG_UPDATE mode?
    9. 2.9  Is there a way to manually control PCHG and PDSG?
    10. 2.10 Can I use an NFET with the PDSG pin?
    11. 2.11 What states are PDSG and PCHG when disabled?
    12. 2.12 How do I disable the Discharge FET (DFET) and Charge FET (CFET)?
    13. 2.13 Can the BQ769x2 idle with PDSG ON during SLEEP mode?
  5. 3 Coulomb Counter (CC) and ADCs FAQs
    1. 3.1  What resolution does the ADC provide for voltage measurement?
    2. 3.2  How fast does the BQ769x2 ADC sample?
    3. 3.3  How does the ADC operates while on SLEEP mode?
    4. 3.4  Does the coulomb counter provide a SoC and SoH measurement?
    5. 3.5  Can the coulomb counter be used to measure instantaneous current?
    6. 3.6  What is the resolution of the coulomb counter?
    7. 3.7  Is the coulomb counter used for overcurrent detection?
    8. 3.8  What is the difference between OCD1, OCD2, OCD3, and SCD?
    9. 3.9  Why is the accumulated charge measurement seems to be producing an incorrect value?
    10. 3.10 Why is the voltage of CELL1 seems to be measuring incorrectly?
  6. 4 Communication Protocols and Programming FAQs
    1. 4.1  What communication protocols does the BQ769x2 support?
    2. 4.2  Does the BQ769x2 support cyclic redundancy checking (CRC)?
    3. 4.3  Does the I 2 C lines require pull-up resistors to operate?
    4. 4.4  Does the BQ769x2 support clock stretching?
    5. 4.5  Does the BQ769x2 allow block writes and reads?
    6. 4.6  Does the BQ769x2 require isolation to communicate?
    7. 4.7  When shall I use OTP programming?
    8. 4.8  How does the BQ769x2 OTP memory work?
    9. 4.9  How many times can the BQ769x2 OTP memory be modified?
    10. 4.10 What hardware is necessary to program the OTP memory?
    11. 4.11 How can the host reset the ALERT pin interrupt?
    12. 4.12 Why is my subcommand returning incorrect data?
  7. 5 Calibration and Temperature Sensing FAQs
    1. 5.1  Does the BQ769x2 come calibrated or do I need to calibrate externally?
    2. 5.2  Can custom calibrations be stored onto the BQ769x2?
    3. 5.3  How do I modify RAM registers to update calibrations?
    4. 5.4  Can each cell measurement have a custom (offset/gain) calibration factor?
    5. 5.5  How to configure a multipurpose pin to work as a thermistor ?
    6. 5.6  How many thermistors does the device support?
    7. 5.7  Can thermal protections be disabled and are thermistors necessary for operation?
    8. 5.8  Why do I need a capacitor across each thermistor?
    9. 5.9  How are the thermistor coefficients calculated for temperature calibration?
    10. 5.10 Why is the thermistor coefficient calculator tool throwing errors?
  8. 6 Cell Balancing FAQs
    1. 6.1 How does cell balancing work?
    2. 6.2 Can all battery cells be balanced simultaneously?
    3. 6.3 Does the BQ769x2 support adjacent cell balancing?
    4. 6.4 How does cell balancing work in RELAX mode?
    5. 6.5 Does the BQ769x2 support external balancing?
    6. 6.6 How large can the current sense resistors be at the VCx input pins?
    7. 6.7 Does cell balancing affect voltage measurement?
    8. 6.8 Why are the cells balancing for different amount of times?
  9. 7 Device Power and State Switching FAQs
    1. 7.1  What is the maximum voltage of battery packs this device support?
    2. 7.2  What is the maximum battery pack voltage allowed when using the charge pump?
    3. 7.3  Is necessary to tie BAT- to VSS?
    4. 7.4  How my other signal GNDs needs to be connected to PACK-?
    5. 7.5  Does a capacitor needs to be placed between VC0 and VC1?
    6. 7.6  What are the recommended typical passive components values for my schematic design?
    7. 7.7  How much current can the two programmable LDOs provide?
    8. 7.8  Can the LDO input transistor be connected to a lower voltage cell on the pack than BAT+ to increase efficiency?
    9. 7.9  In reference designs, why are two capacitors placed between VC16 and PACK+ as well as PACK+ and PACK-?
    10. 7.10 What are the different low power modes of the BQ769x2 device family?
    11. 7.11 How can an MCU know the BQ769x2 is in shutdown?
    12. 7.12 Is disabling the SHUTDOWN mode possible?
    13. 7.13 How does the BQ769x2 exit SHUTDOWN mode?
    14. 7.14 What is soft SHUTDOWN? How can I exit soft SHUTDOWN mode?
  10. 8 Evaluation Modules and BQStudio FAQs
    1. 8.1 Does the BQ769x2 family have any EVMs?
    2. 8.2 How much current the EVM consume while operating?
    3. 8.3 Can I reduce the number of cells enabled on the EVM?
    4. 8.4 Can multiple EVMs connect to one computer when stacking multiple EVMs?
    5. 8.5 Can the device interface with both SMBus and SPI at the same time?
    6. 8.6 Why is BQStudio not detecting to the BQ769x2EVM?
  11. 9 Additional Instructional Material
    1. 9.1 How do I access functional safety documents such as a FMEDA and pin FMEA?
    2. 9.2 Is there any microcontroller code examples for the BQ769x2?
    3. 9.3 Are there any reference designs for the BQ769x2?
    4. 9.4 Is there any documentation on stacking multiple BQ769x2 devices?
    5. 9.5 Where can I find training videos to learn more about battery monitors and protectors?
  12. 10References

7.8 Can the LDO input transistor be connected to a lower voltage cell on the pack than BAT+ to increase efficiency?

No, this configuration is not recommended as hurts the efficiency of battery packs. Since the LDOs can draw up to about 90mA while in operation. Assuming the transistor is connected to the 2nd cell, such that the bottom two cells are pulling an additional 90mA. As the other cells are not seeing this extra current, this results in an imbalance between the cells and require balancing the top 10 or so cells down to match the lower two cells. This generates additional heat as the device balance the remaining cells.