SLUSFC9 December   2023 BQ76972

PRODUCTION DATA  

  1.   1
  2. Features
  3. Applications
  4. Description
  5. Device Comparison Table
  6. Pin Configuration and Functions
  7. Specifications
    1. 6.1  Absolute Maximum Ratings
    2. 6.2  ESD Ratings
    3. 6.3  Recommended Operating Conditions
    4. 6.4  Thermal Information BQ76952
    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 Cell Balancing
    22. 6.22 Cell Open Wire Detector
    23. 6.23 Internal Temperature Sensor
    24. 6.24 Thermistor Measurement
    25. 6.25 Internal Oscillators
    26. 6.26 High-side NFET Drivers
    27. 6.27 Comparator-Based Protection Subsystem
    28. 6.28 Timing Requirements - I2C Interface, 100kHz Mode
    29. 6.29 Timing Requirements - I2C Interface, 400kHz Mode
    30. 6.30 Timing Requirements - HDQ Interface
    31. 6.31 Timing Requirements - SPI Interface
    32. 6.32 Interface Timing Diagrams
    33. 6.33 Typical Characteristics
  8. Detailed Description
    1. 7.1  Overview
    2. 7.2  Functional Block Diagram
    3. 7.3  BQ76972 Device Versions
    4. 7.4  Diagnostics
    5. 7.5  Device Configuration
      1. 7.5.1 Commands and Subcommands
      2. 7.5.2 Configuration Using OTP or Registers
      3. 7.5.3 Device Security
      4. 7.5.4 Scratchpad Memory
    6. 7.6  Measurement Subsystem
      1. 7.6.1  Voltage Measurement
        1. 7.6.1.1 Voltage Measurement Schedule
        2. 7.6.1.2 Usage of VC Pins for Cells Versus Interconnect
        3. 7.6.1.3 Cell 1 Voltage Validation During SLEEP Mode
      2. 7.6.2  General Purpose ADCIN Functionality
      3. 7.6.3  Coulomb Counter and Digital Filters
      4. 7.6.4  Synchronized Voltage and Current Measurement
      5. 7.6.5  Internal Temperature Measurement
      6. 7.6.6  Thermistor Temperature Measurement
      7. 7.6.7  Factory Trim of Voltage ADC
      8. 7.6.8  Cell Voltage Measurement Accuracy
        1. 7.6.8.1 Fixed Offset Adjustment
        2. 7.6.8.2 Cell Offset Calibration
      9. 7.6.9  Voltage Calibration (ADC Measurements)
      10. 7.6.10 Voltage Calibration (COV and CUV Protections)
      11. 7.6.11 Current Calibration
      12. 7.6.12 Temperature Calibration
    7. 7.7  Primary and Secondary Protection Subsystems
      1. 7.7.1 Protections Overview
      2. 7.7.2 Primary Protections
      3. 7.7.3 Secondary Protections
      4. 7.7.4 High-Side NFET Drivers
      5. 7.7.5 Protection FETs Configuration and Control
        1. 7.7.5.1 FET Configuration
        2. 7.7.5.2 PRECHARGE and PREDISCHARGE Modes
      6. 7.7.6 Load Detect Functionality
    8. 7.8  Device Hardware Features
      1. 7.8.1  Voltage References
      2. 7.8.2  ADC Multiplexer
      3. 7.8.3  LDOs
        1. 7.8.3.1 Preregulator Control
        2. 7.8.3.2 REG1 and REG2 LDO Controls
      4. 7.8.4  Standalone Versus Host Interface
      5. 7.8.5  Multifunction Pin Controls
      6. 7.8.6  RST_SHUT Pin Operation
      7. 7.8.7  CFETOFF, DFETOFF, and BOTHOFF Pin Functionality
      8. 7.8.8  ALERT Pin Operation
      9. 7.8.9  DDSG and DCHG Pin Operation
      10. 7.8.10 Fuse Drive
      11. 7.8.11 Cell Open Wire
      12. 7.8.12 Low Frequency Oscillator
      13. 7.8.13 High Frequency Oscillator
    9. 7.9  Device Functional Modes
      1. 7.9.1 Overview
      2. 7.9.2 NORMAL Mode
      3. 7.9.3 SLEEP Mode
      4. 7.9.4 DEEPSLEEP Mode
      5. 7.9.5 SHUTDOWN Mode
      6. 7.9.6 CONFIG_UPDATE Mode
    10. 7.10 Serial Communications Interface
      1. 7.10.1 Serial Communications Overview
      2. 7.10.2 I2C Communications
      3. 7.10.3 SPI Communications
        1. 7.10.3.1 SPI Protocol
      4. 7.10.4 HDQ Communications
    11. 7.11 Cell Balancing
      1. 7.11.1 Cell Balancing Overview
  9. 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. Device and Documentation Support
    1. 9.1 Documentation Support
    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

Package Options

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

Layout Guidelines

  • The quality of the Kelvin connections at the sense resistor is critical. The sense resistor must have a temperature coefficient no greater than 50 ppm in order to minimize current measurement drift with temperature. Choose the value of the sense resistor to correspond to the available overcurrent and short-circuit ranges of the BQ76972 device. Parallel resistors can be used as long as good Kelvin sensing is ensured. The device is designed to support a 1-mΩ sense resistor.
  • In reference to the system circuitry, the following features require attention for component placement and layout: Differential Low-Pass Filter, and I2C communication.
  • The BQ76972 device uses an integrating delta-sigma ADC for current measurements. For best performance, 100-Ω resistors should be included from the sense resistor terminals to the SRP and SRN inputs of the device, with a 0.1-μF filter capacitor placed across the SRP and SRN pins. Optional 0.1-µF filter capacitors can be added for additional noise filtering at each sense input pin to ground. All filter components should be placed as close as possible to the device, rather than close to the sense resistor, and the traces from the sense resistor routed in parallel to the filter circuit. A ground plane can also be included around the filter network to add additional noise immunity.
  • The BQ76972 device internal REG18 LDO requires an external decoupling capacitor, which should be placed as close to the REG18 pin as possible, with minimized trace inductance, and connected to a ground plane electrically connected to VSS.
  • The I2C clock and data pins have integrated ESD protection circuits; however, adding a Zener diode and series resistor on each pin provides more robust ESD performance.