SLUSE86A April   2022  – April 2024 BQ76922

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 BQ76922
    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 Voltage References
    14. 6.14 Coulomb Counter
    15. 6.15 Coulomb Counter Digital Filter (CC1)
    16. 6.16 Current Measurement Digital Filter (CC2)
    17. 6.17 Current Wake Detector
    18. 6.18 Analog-to-Digital Converter
    19. 6.19 Cell Balancing
    20. 6.20 Cell Open Wire Detector
    21. 6.21 Internal Temperature Sensor
    22. 6.22 Thermistor Measurement
    23. 6.23 Internal Oscillators
    24. 6.24 High-side NFET Drivers
    25. 6.25 Comparator-Based Protection Subsystem
    26. 6.26 Timing Requirements – I2C Interface, 100kHz Mode
    27. 6.27 Timing Requirements – I2C Interface, 400kHz Mode
    28. 6.28 Timing Requirements – HDQ Interface
    29. 6.29 Interface Timing Diagrams
    30. 6.30 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 Using 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  Voltage Calibration (ADC Measurements)
      9. 7.5.9  Voltage Calibration (COV and CUV Protections)
      10. 7.5.10 Current Calibration
      11. 7.5.11 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 LDO Control
      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  Fuse Drive
      10. 7.7.10 Cell Open Wire
      11. 7.7.11 Low Frequency Oscillator
      12. 7.7.12 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 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
  10. 9 Power Supply Requirements
  11. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  12. 11Device and Documentation Support
    1. 11.1 Third-Party Products Disclaimer
    2. 11.2 Documentation Support
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  13. 12Revision History
  14. 13Mechanical, Packaging, Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • RSN|32
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.6.4 High-Side NFET Drivers

The BQ76922 device includes an integrated charge pump and high-side NFET drivers for driving CHG and DSG protection FETs. The charge pump uses an external capacitor connected between the BAT and CP1 pins that is charged to an overdrive voltage when the charge pump is enabled. Due to the time required for the charge pump to bring the overdrive voltage on the external CP1 pin to full voltage, it is recommended to leave the charge pump powered whenever it may be needed quickly to drive the CHG or DSG FETs.

The DSG FET driver includes a special option (denoted source follower mode) to drive the DSG FET with the BAT pin voltage during SLEEP mode. This capability is included to provide low power in SLEEP mode, when there is no significant charge or discharge current flowing. It is recommended to keep the charge pump enabled even when the source follower mode is enabled, so whenever a discharge current is detected, the device can quickly transition to driving the DSG FET using the charge pump voltage. The source follower mode is enabled using a configuration setting and is not intended to be used when significant charging or discharging current is flowing, since the FET will exhibit a large drain-source voltage and may undergo excessive heating.

The overdrive level of the charge pump voltage can be set to 5.5V or 11V, based on the configuration setting. In general, the 5.5V setting results in lower power dissipation when a FET is being driven, while the higher 11V overdrive reduces the on-resistance of the FET. If a FET exhibits significant gate leakage current when driven at the higher overdrive level, this can result in a higher device current for the charge pump to support this. In this case, using the lower overdrive level can reduce the leakage current and thus the device current.

The BQ76922 device supports a system with FETs in a series or parallel configuration, where the parallel configuration includes a separate path for the charger connection versus the discharge (load) connection. The control logic for the device operates slightly differently in these two cases, which is set based on the configuration setting.

The FET drivers in the BQ76922 device can be controlled in several different manner, depending on customer requirements:

Fully autonomous
The BQ76922 device can detect protection faults and autonomously disable the FETs, monitor for a recovery condition, and autonomously reenable the FETs, without requiring any host processor involvement.
Partially autonomous
The BQ76922 device can detect protection faults and autonomously disable the FETs. When the host receives an interrupt and recognizes the fault, the host can send commands across the digital communications interface to keep the FETs off until the host decides to release them.
Alternatively, the host can assert the CFETOFF or DFETOFF pins to keep the FETs off. As long as these pins are asserted, the FETs are blocked from being reenabled. When these pins are deasserted, the BQ76922 will reenable the FETs if nothing is blocking them being reenabled (such as fault conditions still present, or the CFETOFF or DFETOFF pins are asserted).
Manual control
The BQ76922 device can detect protection faults and provide an interrupt to a host processor over the ALERT pin. The host processor can read the status information of the fault over the communication bus (if desired) and can quickly force the CHG or DSG FETs off by driving the CFETOFF or DFETOFF pins from the host processor, or commands over the digital communications interface.
When the host decides to allow the FETs to turn on again, it writes the appropriate command or deasserts the CFETOFF and DFETOFF pins, and the BQ76922 device will reenable the FETs if nothing is blocking them being reenabled.