SLUSF60 December   2023 BQ77307

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 BQ77307
    5. 6.5  Supply Current
    6. 6.6  Digital I/O
    7. 6.7  REGOUT LDO
    8. 6.8  Voltage References
    9. 6.9  Current Detector
    10. 6.10 Thermistor Pullup Resistor
    11. 6.11 Hardware Overtemperature Detector
    12. 6.12 Internal Oscillator
    13. 6.13 Charge and Discharge FET Drivers
    14. 6.14 Protection Subsystem
    15. 6.15 Timing Requirements - I2C Interface, 100kHz Mode
    16. 6.16 Timing Requirements - I2C Interface, 400kHz Mode
    17. 6.17 Timing Diagram
    18. 6.18 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Device Configuration
      1. 7.3.1 Commands and Subcommands
      2. 7.3.2 Configuration Using OTP or Registers
      3. 7.3.3 Device Security
    4. 7.4 Device Hardware Features
      1. 7.4.1  Voltage Protection Subsystem
      2. 7.4.2  Current Protection Subsystem
      3. 7.4.3  Unused VC Pins
      4. 7.4.4  Internal Temperature Protection
      5. 7.4.5  Thermistor Temperature Protections
      6. 7.4.6  Protection FET Drivers
      7. 7.4.7  Voltage References
      8. 7.4.8  Multiplexer
      9. 7.4.9  LDOs
      10. 7.4.10 Standalone Versus Host Interface
      11. 7.4.11 ALERT Pin Operation
      12. 7.4.12 Low Frequency Oscillator
      13. 7.4.13 I2C Serial Communications Interface
    5. 7.5 Protection Subsystem
      1. 7.5.1 Protections Overview
      2. 7.5.2 Primary Protections
      3. 7.5.3 Cell Open Wire Protection
      4. 7.5.4 Diagnostic Checks
    6. 7.6 Device Power Modes
      1. 7.6.1 Overview of Power Modes
      2. 7.6.2 NORMAL Mode
      3. 7.6.3 SHUTDOWN Mode
      4. 7.6.4 CONFIG_UPDATE Mode
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Performance Plot
      4. 8.2.4 Random Cell Connection Support
      5. 8.2.5 Startup Timing
      6. 8.2.6 FET Driver Turn-Off
      7. 8.2.7 Usage of Unused Pins
  10. 9 Power Supply Recommendations
  11. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  12. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  13. 12Revision History
  14. 13Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.2 Detailed Design Procedure

  • Determine the number of series cells.
    • This value depends on the cell chemistry and the load requirements of the system. For example, to support a minimum battery voltage of 12 V using Li-CO2 type cells with a cell minimum voltage of 3 V, at least 4-series cells are required.
    • For the correct cell connections, see Section 7.4.3.
  • Protection FET selection and configuration
    • The BQ77307 device is designed for use with low-side NFET protection
    • The configuration should be selected for series versus parallel FETs, which may lead to different FET selection for charge versus discharge direction.
    • These FETs should be rated for the maximum:
      • Voltage, which should be approximately 5 V (DC) to 10 V (peak) per series cell.
      • Current, which should be calculated based on both the maximum DC current and the maximum transient current with some margin.
      • Power Dissipation, which can be a factor of the RDS(ON) rating of the FET, the FET package, and the PCB design.
  • Sense resistor selection
    • The resistance value should be selected to maximize the input range of the SCD, OCD, and OCC protections but not exceed the absolute maximum ratings, and avoid excessive heat generation within the resistor.
      • Using the normal maximum charge or discharge current, the sense resistor = 200 mV / 40.0 A = 5 mΩ maximum.
      • Considering a short circuit discharge current of 80 A, the recommended maximum SRP, SRN voltage of ≈0.75 V, and the maximum SCD threshold of 500 mV, the sense resistor should be below 500 mV / 80 A= 6.25 mΩ maximum.
    • Further tolerance analysis (value tolerance, temperature variation, and so on) and PCB design margin should also be considered, so a sense resistor of 1 mΩ is suitable with a 50-ppm temperature coefficient and power rating of 1 W.
  • The REGOUT is selected to provide the supply for an external host processor and the pullup supply for the I2C bus and ALERT pin, with output voltage selected for 3.3 V.
    • A 1 μF or larger capacitor should be placed at the REGOUT pin.
    • The REGOUT draws its input current from the REGSRC pin. This pin is connected to PACK+ through a series diode and 10 Ω resistor, with a 1-μF capacitor to VSS placed at the REGSRC pin.