SLVSLM6 May   2026 BQ76972-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
  7. 6 Specifications
    1. 6.1  Absolute Maximum Ratings
    2. 6.2  ESD Ratings
    3. 6.3  Recommended Operating Conditions
    4. 6.4  Thermal Information BQ76972-Q1
    5. 6.5  Supply Current
    6. 6.6  Digital I/O
    7. 6.7  LD Pin
    8. 6.8  Precharge (PCHG) and Predischarge (PDSG) FET Drive
    9. 6.9  FUSE Pin Functionality
    10. 6.10 REG18 LDO
    11. 6.11 REG0 Pre-regulator
    12. 6.12 REG1 LDO
    13. 6.13 REG2 LDO
    14. 6.14 Voltage References
    15. 6.15 Coulomb Counter
    16. 6.16 Coulomb Counter Digital Filter (CC1)
    17. 6.17 Current Measurement Digital Filter (CC2)
    18. 6.18 Current Wake Detector
    19. 6.19 Analog-to-Digital Converter
    20. 6.20 Cell Voltage Measurement Accuracy
    21. 6.21 Multifunction Pin ADC Measurement
    22. 6.22 Cell Balancing
    23. 6.23 Cell Open Wire Detector
    24. 6.24 Internal Temperature Sensor
    25. 6.25 Thermistor Measurement
    26. 6.26 Internal Oscillators
    27. 6.27 High-side NFET Drivers
    28. 6.28 Comparator-Based Protection Subsystem
    29. 6.29 Timing Requirements - I2C Interface, 100kHz Mode
    30. 6.30 Timing Requirements - I2C Interface, 400kHz Mode
    31. 6.31 Timing Requirements - HDQ Interface
    32. 6.32 Timing Requirements - SPI Interface
    33. 6.33 Interface Timing Diagrams
    34. 6.34 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1  Overview
    2. 7.2  Functional Block Diagram
    3. 7.3  Diagnostics
    4. 7.4  Device Configuration
      1. 7.4.1 Commands and Subcommands
      2. 7.4.2 Configuration Using OTP or Registers
      3. 7.4.3 Device Security
      4. 7.4.4 Scratchpad Memory
    5. 7.5  Measurement Subsystem
      1. 7.5.1  Voltage Measurement
        1. 7.5.1.1 Voltage Measurement Schedule
        2. 7.5.1.2 Usage of VC Pins for Cells Versus Interconnect
        3. 7.5.1.3 Cell 1 Voltage Validation During SLEEP Mode
      2. 7.5.2  General Purpose ADCIN Functionality
      3. 7.5.3  Coulomb Counter and Digital Filters
      4. 7.5.4  Synchronized Voltage and Current Measurement
      5. 7.5.5  Internal Temperature Measurement
      6. 7.5.6  Thermistor Temperature Measurement
      7. 7.5.7  Factory Trim of Voltage ADC
      8. 7.5.8  Cell Voltage Measurement Accuracy
        1. 7.5.8.1 Cell Offset Calibration
      9. 7.5.9  Voltage Calibration (ADC Measurements)
      10. 7.5.10 Voltage Calibration (COV and CUV Protections)
      11. 7.5.11 Current Calibration
      12. 7.5.12 Temperature Calibration
    6. 7.6  Primary and Secondary Protection Subsystems
      1. 7.6.1 Protections Overview
      2. 7.6.2 Primary Protections
      3. 7.6.3 Secondary Protections
      4. 7.6.4 High-Side NFET Drivers
      5. 7.6.5 Protection FETs Configuration and Control
        1. 7.6.5.1 FET Configuration
        2. 7.6.5.2 PRECHARGE and PREDISCHARGE Modes
      6. 7.6.6 Load Detect Functionality
    7. 7.7  Device Hardware Features
      1. 7.7.1  Voltage References
      2. 7.7.2  ADC Multiplexer
      3. 7.7.3  LDOs
        1. 7.7.3.1 Preregulator Control
        2. 7.7.3.2 REG1 and REG2 LDO Controls
      4. 7.7.4  Standalone Versus Host Interface
      5. 7.7.5  Multifunction Pin Controls
      6. 7.7.6  RST_SHUT Pin Operation
      7. 7.7.7  CFETOFF, DFETOFF, and BOTHOFF Pin Functionality
      8. 7.7.8  ALERT Pin Operation
      9. 7.7.9  DDSG and DCHG Pin Operation
      10. 7.7.10 Fuse Drive
      11. 7.7.11 Cell Open Wire
      12. 7.7.12 Low Frequency Oscillator
      13. 7.7.13 High Frequency Oscillator
    8. 7.8  Device Functional Modes
      1. 7.8.1 Overview
      2. 7.8.2 NORMAL Mode
      3. 7.8.3 SLEEP Mode
      4. 7.8.4 DEEPSLEEP Mode
      5. 7.8.5 SHUTDOWN Mode
      6. 7.8.6 CONFIG_UPDATE Mode
    9. 7.9  Serial Communications Interface
      1. 7.9.1 Serial Communications Overview
      2. 7.9.2 I2C Communications
      3. 7.9.3 SPI Communications
        1. 7.9.3.1 SPI Protocol
      4. 7.9.4 HDQ Communications
    10. 7.10 Cell Balancing
      1. 7.10.1 Cell Balancing Overview
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Design Requirements (Example)
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Performance Plot
      4. 8.2.4 Calibration Process
    3. 8.3 Random Cell Connection Support
    4. 8.4 Startup Timing
    5. 8.5 FET Driver Turn-Off
    6. 8.6 Unused Pins
    7. 8.7 Power Supply Requirements
    8. 8.8 Layout
      1. 8.8.1 Layout Guidelines
      2. 8.8.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Documentation Support
      1. 9.1.1 Related Documentation
    2. 9.2 Support Resources
    3. 9.3 Trademarks
    4. 9.4 Electrostatic Discharge Caution
    5. 9.5 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, Orderable Information

7.9.4 HDQ Communications

The HDQ interface is an asynchronous return-to-one protocol where a processor communicates with the BQ76972-Q1 device using a single-wire connection to the ALERT pin or the HDQ pin, depending on the configuration. The controller (host device) and the responder (the BQ76972-Q1 device) drive the HDQ interface using an open-drain driver with a pullup resistor from the HDQ interface to a supply voltage required on the circuit board. The BQ76972-Q1 device can be changed from the default communication mode to HDQ communication mode by setting the Settings:Configuration:Comm Type configuration register or by sending a subcommand (at which point the device switches to HDQ mode immediately).

Note: The SWAP_COMM_MODE() subcommand immediately changes the communications interface to that selected by the Comm Type configuration, while the SWAP_TO_HDQ() subcommand immediately changes the interface to HDQ using the ALERT pin.

With HDQ, the least significant bit (LSB) of a data byte (command) or word (data) is transmitted first.

The 8-bit command code consists of two fields: the 7-bit HDQ command code (bits 0–6) and the 1-bit R/W field (MSB Bit 7). The R/W field directs the device to do one of the following:

  • Accept the next 8 bits as data from the host to the device or
  • Output 8 bits of data from the device to the host in response to the 7-bit command.

The HDQ peripheral on the BQ76972-Q1 device can transmit and receive data as an HDQ responder only.

The return-to-one data bit frame of HDQ consists of the following sections:

  1. The first section is used to start the transmission by the host sending a Break (the host drives the HDQ interface to a logic-low state for a time t(B)) followed by a Break Recovery (the host releases the HDQ interface for a time t(BR)).
  2. The next section is for host command transmission, where the host transmits 8 bits by driving the HDQ interface for 8 T(CYCH) time slots. For each time slot, the HDQ line is driven low for a time T(HW0) (host writing a "0") or T(HW1) (host writing a "1"). The HDQ pin is then released and remains high to complete each T(CYCH) time slot.
  3. The next section is for data transmission where the host (if a write was initiated) or device (if a read was initiated) transmits 8 bits by driving the HDQ interface for 8 T(CYCH) (if host is driving) or T(CYCD) (if device is driving) time slots. The HDQ line is driven low for a time T(HW0) (host writing a "0"), T(HW1) (host writing a "1"), T(DW0) (device writing a "0"), or T(DW1) (device writing a "1"). The HDQ pin is then released and remains high to complete the time slot. The HDQ interface does not auto-increment, so a separate transaction must be sent for each byte to be transferred.