SLUSCU0I March   2018  – September 2020 BQ77915

PRODUCTION DATA  

  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. 9.3.2.1  Operation in OV
        2. 9.3.2.2  Operation in UV
        3. 9.3.2.3  Operation in OW
        4. 9.3.2.4  Operation in OCD1
        5. 9.3.2.5  Operation in OCD2
        6. 9.3.2.6  Programming the OCD1/2 Delay Using the OCDP Pin
        7. 9.3.2.7  Operation in SCD
        8. 9.3.2.8  Operation in OCC
        9. 9.3.2.9  Overcurrent Recovery Timer
        10. 9.3.2.10 Load Detection and Load Removal Detection
        11. 9.3.2.11 Operation in OTC
        12. 9.3.2.12 Operation in OTD
        13. 9.3.2.13 Operation in UTC
        14. 9.3.2.14 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. 9.3.7.1 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. 9.4.1.1 Power On Reset (POR)
        2. 9.4.1.2 NORMAL Mode
        3. 9.4.1.3 FAULT Mode
        4. 9.4.1.4 HIBERNATE Mode
        5. 9.4.1.5 SHUTDOWN Mode
        6. 9.4.1.6 Customer Fast Production Test Modes
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Recommended System Implementation
        1. 10.1.1.1 CHG and DSG FET Rise and Fall Time
        2. 10.1.1.2 Protecting CHG and LD
        3. 10.1.1.3 Protecting the CHG FET
        4. 10.1.1.4 Using Load Detect for UV Fault Recovery
        5. 10.1.1.5 Temperature Protection
        6. 10.1.1.6 Adding RC Filters to the Sense Resistor
        7. 10.1.1.7 Using the State Comparator in an Application
          1. 10.1.1.7.1 Examples
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 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

CHG FET Driver Operation

The CHG pin is driven high only when no related faults (OV, OW, OTC, UTC, OTD, UTD, OCD1, OCD2, SCD, OCC, and CTRC disabled) are present and the pack is not in HIBERNATE mode of operation. The CHG pin is used to drive the CHG FET, which is designed to be used on the single device configuration or used by the bottom device in a stack configuration.

Turning off the CHG pin has no influence on the overcurrent protection circuitry. The CHG pin is designed to turn on very quickly; the internal on resistance is about 2 kΩ. The CHG FET turn off relies on the external resistor connected in parallel to the gate-source nodes of the NCH power FET.

The CHG FET may be turned on to protect the FET's body diode if the pack is charging, even if a charging inhibit fault condition is present. This is done through the state comparator. The state comparator (with VSTATE_D threshold and VSTATE_D_HYS hysteresis) remains on for the entire duration of a DSG fault with no CHG fault event.

  • If (SRP–SRN) > (VSTATE_D + VSTATE_D_HYS) and no discharge event is detected, the CHG FET output will remain OFF due to the presence of a CHG fault.
  • If (SRP–SRN) ≤ VSTATE_D and a discharge event is detected, the CHG FET output will turn ON for body diode protection.

The CHGFET_OFF signal is a result of the presence of any related faults as shown in Figure 9-9.

GUID-257AD293-51C1-453E-B6E9-2C71AC9B648D-low.gifFigure 9-9 Faults that Can Qualify CHGFET OFF