SLUSCU0I March   2018  – September 2020 BQ77915


  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Description (continued)
  6. Device Comparison Table
  7. Pin Configuration and Functions
    1.     Pin Functions
  8. Specifications
    1. 8.1 Absolute Maximum Ratings
    2. 8.2 ESD Ratings
    3. 8.3 Recommended Operating Conditions
    4. 8.4 Thermal Table
    5. 8.5 Electrical Characteristics
    6. 8.6 Typical Characteristics
  9. Detailed Description
    1. 9.1 Overview
      1. 9.1.1 Device Functionality Summary
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1  Protection Summary
      2. 9.3.2  Fault Operation
        1.  Operation in OV
        2.  Operation in UV
        3.  Operation in OW
        4.  Operation in OCD1
        5.  Operation in OCD2
        6.  Programming the OCD1/2 Delay Using the OCDP Pin
        7.  Operation in SCD
        8.  Operation in OCC
        9.  Overcurrent Recovery Timer
        10. Load Detection and Load Removal Detection
        11. Operation in OTC
        12. Operation in OTD
        13. Operation in UTC
        14. Operation in UTD
      3. 9.3.3  Protection Response and Recovery Summary
      4. 9.3.4  Cell Balancing
      5. 9.3.5  HIBERNATE Mode Operation
      6. 9.3.6  Configuration CRC Check and Comparator Built-In-Self-Test
      7. 9.3.7  Fault Detection Method
        1. Filtered Fault Detection
      8. 9.3.8  State Comparator
      9. 9.3.9  DSG FET Driver Operation
      10. 9.3.10 CHG FET Driver Operation
      11. 9.3.11 External Override of CHG and DSG Drivers
      12. 9.3.12 Configuring 3-Series, 4-Series, or 5-Series Modes
      13. 9.3.13 Stacking Implementations
      14. 9.3.14 Zero-Volt Battery Charging Inhibition
    4. 9.4 Device Functional Modes
      1. 9.4.1 Power Modes
        1. Power On Reset (POR)
        2. NORMAL Mode
        3. FAULT Mode
        4. HIBERNATE Mode
        5. SHUTDOWN Mode
        6. Customer Fast Production Test Modes
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Recommended System Implementation
        1. CHG and DSG FET Rise and Fall Time
        2. Protecting CHG and LD
        3. Protecting the CHG FET
        4. Using Load Detect for UV Fault Recovery
        5. Temperature Protection
        6. Adding RC Filters to the Sense Resistor
        7. Using the State Comparator in an Application
          1. Examples
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. Design Example
      3. 10.2.3 Application Curves
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Documentation Support
      1. 13.1.1 Related Documentation
    2. 13.2 Receiving Notification of Documentation Updates
    3. 13.3 Support Resources
    4. 13.4 Trademarks
    5. 13.5 Electrostatic Discharge Caution
    6. 13.6 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

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

As an example, using a 5-Ah battery, with 1C-rate (5 A) charge and 2C-rate (10 A) discharge, the sense resistor is mostly 3 mΩ or less.

The typical current to turn on the FET body diode protection is 625 mA using this example. The typical current to turn off the FET body diode protection with the 3-mΩ sense resistor is 417 mA. Using this example, a > 1 A current, either charge or discharge should provide a solid FET body diode protection detection. A momentary drop through the hysteresis threshold will not cause the body diode protection to drop, but drops of 2 ms or more will cause the FET to toggle.

Observe the device behavior during an OV event (and no other fault is detected). In an OV event, the CHG FET is off and the DSG FET is on. If a discharge of >1 A occurs, the device would turn on the CHG FET to allow the full discharge current to pass through. Once the overcharged cell is discharged to the OV recovery level, the OV fault is recovered and CHG driver turns on (or remains on in this scenario) and the state comparator is turned off.

If the discharge current drops below the V(STATE_D_HYS) threshold for longer than tSTATE when the device is still in an OV fault, the CHG FET may toggle on and off until the overcharged cell voltage is reduced down to the OV recovery level. When the OV fault recovered, the CHG FET will be turned on solidly and the state comparator is off.

Without the FET body diode protection, if a discharge occurs during an OV fault state, the discharge current can only pass through the CHG FET body diode until the OV fault is recovered. This increases the risk of damaging the CHG FET if the MOSFET is not rated to sustain such current through its body diode. It also increases the FET temperature as current is now carried through the body diode.