SLUSE14B December   2020  – December 2021 BQ76942

PRODUCTION DATA  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Device Comparison Table
  6. Pin Configuration and Functions
  7. Specifications
    1. 7.1  Absolute Maximum Ratings
    2. 7.2  ESD Ratings
    3. 7.3  Recommended Operating Conditions
    4. 7.4  Thermal Information BQ76942
    5. 7.5  Supply Current
    6. 7.6  Digital I/O
    7. 7.7  LD Pin
    8. 7.8  Precharge (PCHG) and Predischarge (PDSG) FET Drive
    9. 7.9  FUSE Pin Functionality
    10. 7.10 REG18 LDO
    11. 7.11 REG0 Pre-regulator
    12. 7.12 REG1 LDO
    13. 7.13 REG2 LDO
    14. 7.14 Voltage References
    15. 7.15 Coulomb Counter
    16. 7.16 Coulomb Counter Digital Filter (CC1)
    17. 7.17 Current Measurement Digital Filter (CC2)
    18. 7.18 Current Wake Detector
    19. 7.19 Analog-to-Digital Converter
    20. 7.20 Cell Balancing
    21. 7.21 Cell Open Wire Detector
    22. 7.22 Internal Temperature Sensor
    23. 7.23 Thermistor Measurement
    24. 7.24 Internal Oscillators
    25. 7.25 High-Side NFET Drivers
    26. 7.26 Comparator-Based Protection Subsystem
    27. 7.27 Timing Requirements – I2C Interface, 100kHz Mode
    28. 7.28 Timing Requirements – I2C Interface, 400kHz Mode
    29. 7.29 Timing Requirements – HDQ Interface
    30. 7.30 Timing Requirements – SPI Interface
    31. 7.31 Interface Timing Diagrams
    32. 7.32 Typical Characteristics
  8. Device Description
    1. 8.1 Overview
    2. 8.2 BQ76942 Device Versions
    3. 8.3 Functional Block Diagram
    4. 8.4 Diagnostics
  9. Device Configuration
    1. 9.1 Commands and Subcommands
    2. 9.2 Configuration Using OTP or Registers
    3. 9.3 Device Security
    4. 9.4 Scratchpad Memory
  10. 10Measurement Subsystem
    1. 10.1  Voltage Measurement
      1. 10.1.1 Voltage Measurement Schedule
      2. 10.1.2 Usage of VC Pins for Cells Versus Interconnect
      3. 10.1.3 Cell 1 Voltage Validation During SLEEP Mode
    2. 10.2  General Purpose ADCIN Functionality
    3. 10.3  Coulomb Counter and Digital Filters
    4. 10.4  Synchronized Voltage and Current Measurement
    5. 10.5  Internal Temperature Measurement
    6. 10.6  Thermistor Temperature Measurement
    7. 10.7  Factory Trim of Voltage ADC
    8. 10.8  Voltage Calibration (ADC Measurements)
    9. 10.9  Voltage Calibration (COV and CUV Protections)
    10. 10.10 Current Calibration
    11. 10.11 Temperature Calibration
  11. 11Primary and Secondary Protection Subsystems
    1. 11.1 Protections Overview
    2. 11.2 Primary Protections
    3. 11.3 Secondary Protections
    4. 11.4 High-Side NFET Drivers
    5. 11.5 Protection FETs Configuration and Control
      1. 11.5.1 FET Configuration
      2. 11.5.2 PRECHARGE and PREDISCHARGE Modes
    6. 11.6 Load Detect Functionality
  12. 12Device Hardware Features
    1. 12.1  Voltage References
    2. 12.2  ADC Multiplexer
    3. 12.3  LDOs
      1. 12.3.1 Preregulator Control
      2. 12.3.2 REG1 and REG2 LDO Controls
    4. 12.4  Standalone Versus Host Interface
    5. 12.5  Multifunction Pin Controls
    6. 12.6  RST_SHUT Pin Operation
    7. 12.7  CFETOFF, DFETOFF, BOTHOFF Pin Functionality
    8. 12.8  ALERT Pin Operation
    9. 12.9  DDSG and DCHG Pin Operation
    10. 12.10 Fuse Drive
    11. 12.11 Cell Open Wire
    12. 12.12 Low Frequency Oscillator
    13. 12.13 High Frequency Oscillator
  13. 13Device Functional Modes
    1. 13.1 Overview
    2. 13.2 NORMAL Mode
    3. 13.3 SLEEP Mode
    4. 13.4 DEEPSLEEP Mode
    5. 13.5 SHUTDOWN Mode
    6. 13.6 CONFIG_UPDATE Mode
  14. 14Serial Communications Interface
    1. 14.1 Serial Communications Overview
    2. 14.2 I2C Communications Subsystem
    3. 14.3 SPI Communications Interface
      1. 14.3.1 SPI Protocol
    4. 14.4 HDQ Communications Interface
  15. 15Cell Balancing
    1. 15.1 Cell Balancing Overview
  16. 16Application and Implementation
    1. 16.1 Application Information
    2. 16.2 Typical Applications
      1. 16.2.1 Design Requirements (Example)
      2. 16.2.2 Detailed Design Procedure
      3. 16.2.3 Application Performance Plot
      4. 16.2.4 Calibration Process
      5. 16.2.5 Design Example
    3. 16.3 Random Cell Connection Support
    4. 16.4 Startup Timing
    5. 16.5 FET Driver Turn-Off
    6. 16.6 Unused Pins
  17. 17Power Supply Requirements
  18. 18Layout
    1. 18.1 Layout Guidelines
    2. 18.2 Layout Example
  19. 19Device and Documentation Support
    1. 19.1 Third-Party Products Disclaimer
    2. 19.2 Documentation Support
      1. 19.2.1 Receiving Notification of Documentation Updates
    3. 19.3 Support Resources
    4. 19.4 Trademarks
    5. 19.5 Electrostatic Discharge Caution
    6. 19.6 Glossary
  20. 20Mechanical, Packaging, Orderable Information

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HDQ Communications Interface

The HDQ interface is an asynchronous return-to-one protocol where a processor communicates with the BQ76942 device using a single-wire connection to the ALERT pin or the HDQ pin, depending on configuration. Both the controller (host device) and responder (BQ76942) 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 BQ76942 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 BQ76942 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.