SLUUCJ0 November   2023 BQ76907

 

  1.   1
  2.   Read This First
    1.     About This Manual
    2.     Battery Notational Conventions
    3.     Trademarks
    4.     Glossary
  3. Introduction
  4. Device Description
    1. 2.1 Overview
    2. 2.2 Functional Block Diagram
  5. Device Configuration
    1. 3.1 Direct Commands and Subcommands
    2. 3.2 Configuration Using OTP or Registers
    3. 3.3 Data Formats
      1. 3.3.1 Unsigned Integer
      2. 3.3.2 Integer
      3. 3.3.3 Hex
  6. Device Security
  7. Measurement Subsystem
    1. 5.1 Voltage Measurement
      1. 5.1.1 Voltage Measurement Schedule
      2. 5.1.2 Unused VC Cell Input Pins
      3. 5.1.3 General Purpose ADCIN Functionality
    2. 5.2 Coulomb Counter and Digital Filters
    3. 5.3 Internal Temperature Measurement
    4. 5.4 Thermistor Temperature Measurement
    5. 5.5 Measurement Calibration
  8. Protection Subsystem
    1. 6.1  Protections Overview
    2. 6.2  Protection FET Drivers
    3. 6.3  Cell Overvoltage Protection
    4. 6.4  Cell Undervoltage Protection
    5. 6.5  Short Circuit in Discharge Protection
    6. 6.6  Overcurrent in Charge Protection
    7. 6.7  Overcurrent in Discharge 1 and 2 Protections
    8. 6.8  Current Protection Latch
    9. 6.9  CHG Detector
    10. 6.10 Overtemperature in Charge Protection
    11. 6.11 Overtemperature in Discharge Protection
    12. 6.12 Internal Overtemperature Protection
    13. 6.13 Undertemperature in Charge Protection
    14. 6.14 Undertemperature in Discharge Protection
    15. 6.15 Host Watchdog Protection
    16. 6.16 Cell Open Wire Detection
    17. 6.17 Voltage Reference Measurement Diagnostic Protection
    18. 6.18 VSS Measurement Diagnostic Protection
    19. 6.19 REGOUT Diagnostic Protection
    20. 6.20 LFO Oscillator Integrity Diagnostic Protection
    21. 6.21 Internal Factory Trim Diagnostic Protection
  9. Device Status and Controls
    1. 7.1 0x00 Control Status() and 0x12 Battery Status() Commands
    2. 7.2 LDOs
    3. 7.3 ALERT Pin Operation
    4. 7.4 TS Pin Operation
    5. 7.5 Programmable Timer
    6. 7.6 Device Event Timing
  10. Operational Modes
    1. 8.1 Overview of Operational Modes
    2. 8.2 NORMAL Mode
    3. 8.3 SLEEP Mode
    4. 8.4 DEEPSLEEP Mode
    5. 8.5 SHUTDOWN Mode
    6. 8.6 CONFIG_UPDATE Mode
  11. I2C Serial Communications
    1. 9.1 I2C Serial Communications Interface
  12. 10Cell Balancing
    1. 10.1 Cell Balancing
  13. 11Commands and Subcommands
    1. 11.1 Direct Commands
    2. 11.2 Bit field Definitions for Direct Commands
      1. 11.2.1  Safety Alert A Register
      2. 11.2.2  Safety Status A Register
      3. 11.2.3  Safety Alert B Register
      4. 11.2.4  Safety Status B Register
      5. 11.2.5  Battery Status Register
      6. 11.2.6  Alarm Status Register
      7. 11.2.7  Alarm Raw Status Register
      8. 11.2.8  Alarm Enable Register
      9. 11.2.9  FET CONTROL Register
      10. 11.2.10 REGOUT CONTROL Register
      11. 11.2.11 DSG FET Driver PWM Control Register
      12. 11.2.12 CHG FET Driver PWM Control Register
    3. 11.3 Command-only Subcommands
    4. 11.4 Subcommands with Data
    5. 11.5 Bit field Definitions for Subcommands
      1. 11.5.1 DEVICE NUMBER Register
      2. 11.5.2 FW VERSION Register
      3. 11.5.3 HW VERSION Register
      4. 11.5.4 SECURITY KEYS Register
      5. 11.5.5 CB ACTIVE CELLS Register
      6. 11.5.6 PROG TIMER Register
      7. 11.5.7 PROT RECOVERY Register
  14. 12Data Memory
    1. 12.1 Calibration
      1. 12.1.1 Calibration:Voltage
        1. 12.1.1.1 Calibration:Voltage:Cell 1 Gain
        2. 12.1.1.2 Calibration:Voltage:Cell 2 Gain Delta
        3. 12.1.1.3 Calibration:Voltage:Cell 3 Gain Delta
        4. 12.1.1.4 Calibration:Voltage:Cell 4 and 5 Gain Delta
        5. 12.1.1.5 Calibration:Voltage:Cell 6 and 7 Gain Delta
        6. 12.1.1.6 Calibration:Voltage:Stack Gain
      2. 12.1.2 Calibration:Current
        1. 12.1.2.1 Calibration:Current:Curr Gain
        2. 12.1.2.2 Calibration:Current:Curr Offset
        3. 12.1.2.3 Calibration:Current:CC1 Gain
        4. 12.1.2.4 Calibration:Current:CC1 Offset
      3. 12.1.3 Calibration:Temperature
        1. 12.1.3.1 Calibration:Temperature:TS Offset
        2. 12.1.3.2 Calibration:Temperature:Int Temp Gain
        3. 12.1.3.3 Calibration:Temperature:Int Temp Offset
    2. 12.2 Settings
      1. 12.2.1 Settings:Configuration
        1. 12.2.1.1 Settings:Configuration:Power Config
        2. 12.2.1.2 Settings:Configuration:REGOUT Config
        3. 12.2.1.3 Settings:Configuration:I2C Address
        4. 12.2.1.4 Settings:Configuration:I2C Config
        5. 12.2.1.5 Settings:Configuration:DA Config
        6. 12.2.1.6 Settings:Configuration:Vcell Mode
        7. 12.2.1.7 Settings:Configuration:Default Alarm Mask
        8. 12.2.1.8 Settings:Configuration:FET Options
        9. 12.2.1.9 Settings:Configuration:Charge Detector Time
      2. 12.2.2 Settings:Cell Balancing
        1. 12.2.2.1 Settings:Cell Balancing:Balancing Configuration
        2. 12.2.2.2 Settings:Cell Balancing:Min Temp Threshold
        3. 12.2.2.3 Settings:Cell Balancing:Max Temp Threshold
        4. 12.2.2.4 Settings:Cell Balancing:Max Internal Temp
      3. 12.2.3 Settings:Protection
        1. 12.2.3.1 Settings:Protection:Enabled Protections A
        2. 12.2.3.2 Settings:Protection:Enabled Protections B
        3. 12.2.3.3 Settings:Protection:DSG FET Protections A
        4. 12.2.3.4 Settings:Protection:CHG FET Protections A
        5. 12.2.3.5 Settings:Protection:Both FET Protections B
        6. 12.2.3.6 Settings:Protection:Body Diode Threshold
        7. 12.2.3.7 Settings:Protection:Cell Open Wire NORMAL Check Time
        8. 12.2.3.8 Settings:Protection:Cell Open Wire SLEEP Check Time
        9. 12.2.3.9 Settings:Protection:Host Watchdog Timeout
    3. 12.3 Protections
      1. 12.3.1 Protections:Cell Voltage
        1. 12.3.1.1 Protections:Cell Voltage:Cell Undervoltage Protection Threshold
        2. 12.3.1.2 Protections:Cell Voltage:Cell Undervoltage Protection Delay
        3. 12.3.1.3 Protections:Cell Voltage:Cell Undervoltage Protection Recovery Hysteresis
        4. 12.3.1.4 Protections:Cell Voltage:Cell Overvoltage Protection Threshold
        5. 12.3.1.5 Protections:Cell Voltage:Cell Overvoltage Protection Delay
        6. 12.3.1.6 Protections:Cell Voltage:Cell Overvoltage Protection Recovery Hysteresis
      2. 12.3.2 Protections:Current
        1. 12.3.2.1  Protections:Current:Overcurrent in Charge Protection Threshold
        2. 12.3.2.2  Protections:Current:Overcurrent in Charge Protection Delay
        3. 12.3.2.3  Protections:Current:Overcurrent in Discharge 1 Protection Threshold
        4. 12.3.2.4  Protections:Current:Overcurrent in Discharge 1 Protection Delay
        5. 12.3.2.5  Protections:Current:Overcurrent in Discharge 2 Protection Threshold
        6. 12.3.2.6  Protections:Current:Overcurrent in Discharge 2 Protection Delay
        7. 12.3.2.7  Protections:Current:Short Circuit in Discharge Protection Threshold
        8. 12.3.2.8  Protections:Current:Short Circuit in Discharge Protection Delay
        9. 12.3.2.9  Protections:Current:Latch Limit
        10. 12.3.2.10 Protections:Current:Recovery Time
      3. 12.3.3 Protections:Temperature
        1. 12.3.3.1  Protections:Temperature:Overtemperature in Charge Protection Threshold
        2. 12.3.3.2  Protections:Temperature:Overtemperature in Charge Protection Delay
        3. 12.3.3.3  Protections:Temperature:Overtemperature in Charge Protection Recovery
        4. 12.3.3.4  Protections:Temperature:Undertemperature in Charge Protection Threshold
        5. 12.3.3.5  Protections:Temperature:Undertemperature in Charge Protection Delay
        6. 12.3.3.6  Protections:Temperature:Undertemperature in Charge Protection Recovery
        7. 12.3.3.7  Protections:Temperature:Overtemperature in Discharge Protection Threshold
        8. 12.3.3.8  Protections:Temperature:Overtemperature in Discharge Protection Delay
        9. 12.3.3.9  Protections:Temperature:Overtemperature in Discharge Protection Recovery
        10. 12.3.3.10 Protections:Temperature:Undertemperature in Discharge Protection Threshold
        11. 12.3.3.11 Protections:Temperature:Undertemperature in Discharge Protection Delay
        12. 12.3.3.12 Protections:Temperature:Undertemperature in Discharge Protection Recovery
        13. 12.3.3.13 Protections:Temperature:Internal Overtemperature Protection Threshold
        14. 12.3.3.14 Protections:Temperature:Internal Overtemperature Protection Delay
        15. 12.3.3.15 Protections:Temperature:Internal Overtemperature Protection Recovery
    4. 12.4 Power
      1. 12.4.1 Power:Sleep
        1. 12.4.1.1 Power:Sleep:Sleep Current
        2. 12.4.1.2 Power:Sleep:Voltage Time
        3. 12.4.1.3 Power:Sleep:Wake Comparator Current
      2. 12.4.2 Power:Shutdown
        1. 12.4.2.1 Power:Shutdown:Shutdown Cell Voltage
        2. 12.4.2.2 Power:Shutdown:Shutdown Stack Voltage
        3. 12.4.2.3 Power:Shutdown:Shutdown Temperature
        4. 12.4.2.4 Power:Shutdown:Auto Shutdown Time
    5. 12.5 Security
      1. 12.5.1 Security:Settings
        1. 12.5.1.1 Security:Settings:Security Settings
        2. 12.5.1.2 Security:Settings:Full Access Key Step 1
        3. 12.5.1.3 Security:Settings:Full Access Key Step 2
    6. 12.6 Data Memory Summary
  15. 13Revision History

Cell Open Wire Detection

The BQ76907 device supports detecting a disconnection between a cell in the pack and the cell attachment to the PCB containing BQ76907. Without this check, the voltage at the cell input pin of the BQ76907 device can persist for some time on the board-level capacitor, leading to incorrect voltage readings. The Cell Open Wire detection in the BQ76907 device operates by enabling a small current source from each cell to VSS at programmable intervals. If a cell input pin is floating due to an open wire condition, this current discharges the capacitance, causing the voltage at the pin to slowly drop. This drop in voltage can eventually trigger a Cell Undervoltage protection fault on that particular cell, as well as a Cell Overvoltage protection fault on the cell above it. It is important that the cell undervoltage and overvoltage protections be enabled with appropriate threshold settings for the open wire condition to be detected and the desired reaction initiated.

In NORMAL mode the cell open wire current is enabled, one cell at a time, one cell approximately every ADSCAN, then disabled for COWNTIME FULLSCAN intervals. The parameter COWNTIME is set by the Settings:Protection:Cell Open-Wire NORMAL Check Time configuration register, and a setting of 0 disables this check entirely. The current source at each cell is only enabled during the Shared Slot measurement (which is programmable in width from 366 μs to 2.93 ms), except that it skips a Shared Slot being used to measure the stack voltage, to avoid corrupting the stack voltage measurement. Only one current source is enabled in one ADSCAN, so in a 7s system it requires 8 or 9 ADSCAN intervals to have the current source at each cell enabled (depending on the skipped slots), then the current sources are all disabled for COWNTIME FULLSCAN intervals, before the loop repeats.

This provides programmability in the average current drawn from approximately 2 nA to approximately 2 μA in NORMAL mode, based on the typical current source value of 55 µA. During SLEEP mode, the cell open wire current source is enabled immediately following the last burst measurement slot in immediate sequence for each cell in selected burst measurements, for the duration of a Shared Slot per cell. The selection of burst measurements is based on the Settings:Protection:Cell Open-Wire SLEEP Check Time[COWSTIME2:0]. The cell open-wire currents can be enabled or disabled in SLEEP mode using the Settings:Protection:Cell Open-Wire SLEEP Check Time[COWSEN] configuration bit.

Table 6-19 Cell Open-Wire SLEEP Check Time Settings
Bit Setting COWSTIME[2:0]Description
0x0Current sources are activated once every 8 burst measurements
0x1Current sources are activated once every 4 burst measurements
0x2Current sources are activated once every 2 burst measurements
0x3Current sources are activated once every burst measurement
0x4Current sources are activated twice every burst measurement
0x5Current sources are activated four times every burst measurement
0x6Current sources are activated 8 times every burst measurement
0x7Current sources are activated 16 times every burst measurement
Note: The cell open wire check can create a cell imbalance, so select the settings appropriately.

The turn-on and turn-off of the cell open-wire current source creates a transient at the cell voltage input, and depending on the RC time constant of the input components used at the VC input pins, the transient can affect the accuracy of the Cell 1 measurement in NORMAL mode, which occurs immediately after the Shared Slot when the current source is enabled. To overcome this issue, the BQ76907 includes a programmable delay which is inserted between the end of each Shared Slot and the beginning of the cell measurements, to allow sufficient settling for this transient. This delay can be set from 0 to 64 ms by the Settings:Protection:Cell Open-Wire SLEEP Check Time[COWDLY] configuration parameter, which has a default of 1 ms.