SLUSCM3K June   2016  – July 2020 BQ77904 , BQ77905

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
      1. 8.1.1 Device Functionality Summary
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Protection Summary
      2. 8.3.2  Fault Operation
        1. 8.3.2.1  Operation in OV
        2. 8.3.2.2  Operation in UV
        3. 8.3.2.3  Operation in OW
        4. 8.3.2.4  Operation in OCD1
        5. 8.3.2.5  Operation in OCD2
        6. 8.3.2.6  Operation in SCD
        7. 8.3.2.7  Overcurrent Recovery Timer
        8. 8.3.2.8  Load Removal Detection
        9. 8.3.2.9  Load Removal Detection in UV
        10. 8.3.2.10 Operation in OTC
        11. 8.3.2.11 Operation in OTD
        12. 8.3.2.12 Operation in UTC
        13. 8.3.2.13 Operation in UTD
      3. 8.3.3  Protection Response and Recovery Summary
      4. 8.3.4  Configuration CRC Check and Comparator Built-In-Self-Test
      5. 8.3.5  Fault Detection Method
        1. 8.3.5.1 Filtered Fault Detection
      6. 8.3.6  State Comparator
      7. 8.3.7  DSG FET Driver Operation
      8. 8.3.8  CHG FET Driver Operation
      9. 8.3.9  External Override of CHG and DSG Drivers
      10. 8.3.10 Configuring 3-S, 4-S, or 5-S Mode
      11. 8.3.11 Stacking Implementations
      12. 8.3.12 Zero-Volt Battery Charging Inhibition
    4. 8.4 Device Functional Modes
      1. 8.4.1 Power Modes
        1. 8.4.1.1 Power-On Reset (POR)
        2. 8.4.1.2 FAULT Mode
        3. 8.4.1.3 SHUTDOWN Mode
        4. 8.4.1.4 Customer Fast Production Test Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Recommended System Implementation
        1. 9.1.1.1 CHG and DSG FET Rise and Fall Time
        2. 9.1.1.2 Protecting CHG and LD
        3. 9.1.1.3 Protecting CHG FET
        4. 9.1.1.4 Using Load Detect for UV Fault Recovery
        5. 9.1.1.5 Temperature Protection
        6. 9.1.1.6 Adding Filter to Sense Resistor
        7. 9.1.1.7 Using a State Comparator in an Application
          1. 9.1.1.7.1 Examples
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Design Example
      3. 9.2.3 Application Curves
    3. 9.3 System Examples
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Links
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Support Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

8.3.8 CHG FET Driver Operation

The CHG and CHGU pins are driven high only when no related faults (OV, OW, OTC, UTC, OTD, UTD, OCD1, OCD2, SCD, and CTRC are disabled) are present or the pack has a discharge current where (SRP-SRN) < VSTATE_D1 . The CHG pin drives the CHG FET, which is for use on the single device configuration or by the bottom device in a stack configuration. The CHGU pin has the same logic state as the CHG pin and is for use in the upper device (in a multi-stack configuration) to provide the drive signal to the CTRC pin of the lower device. The CHGU pin should never connect to the CHG FET directly.

Turning off the CHG pin has no influence on the overcurrent protection circuitry. The CHG pin is designed to switch on quickly and the target on resistance is about 2 kΩ. When the pin is turned off, the CHG driver pin is actively driven low and will fall together with PACK–.

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

  • If (SRP-SRN) > VSTATE_D and no discharge event is detected, the CHG FET output will remain OFF due to the present of a CHG fault.
  • If (SRP-SRN) ≤ VSTATE_D and a charge 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 8-7.

GUID-6CA8F976-9E1B-4670-890E-A9902AAC3FF0-low.gifFigure 8-7 Faults That Can Qualify CHGFET OFF