SLUSB15J September   2012  – May 2021 BQ2947

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and 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 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Pin Details
        1. 8.3.1.1 Input Sense Voltage, Vx
        2. 8.3.1.2 Output Drive, OUT
        3. 8.3.1.3 Supply Input, VDD
        4. 8.3.1.4 External Delay Capacitor, CD
    4. 8.4 Device Functional Modes
      1. 8.4.1 NORMAL Mode
      2. 8.4.2 OVERVOLTAGE Mode
      3. 8.4.3 Customer Test Mode
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Application Configuration for Active High
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Third-Party Products Disclaimer
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Receiving Notification of Documentation Updates
    4. 12.4 Support Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

8.3 Feature Description

In the BQ2947 family of devices, if any cell voltage exceeds the programmed OV value, a timer circuit is activated. This timer circuit charges the CD pin to a nominal value, then slowly discharges it with a fixed current back down to VSS. When the CD pin falls below a nominal threshold near VSS, the OUT terminal goes from inactive to active state. Additionally, a timeout detection circuit checks to ensure that the CD pin successfully begins charging to above VSS and subsequently drops back down to VSS, and if a timeout error is detected in either direction, it will similarly trigger the OUT pin to become active. See Figure 8-2 for details on CD and OUT pin behavior during an overvoltage event.

For an NCH Open Drain Active Low configuration, the OUT pin pulls down to VSS when active (OV present) and is high impedance when inactive (no OV).

GUID-E4D43153-CCE7-4264-91DE-4EEEE107ACF6-low.gifFigure 8-1 Timing for Overvoltage Sensing (OUT Pin Is Active High)

Figure 8-2 shows the behavior of CD pin during an OV sequence.

GUID-F147765A-E223-435B-94F0-9F084AB159A3-low.gifFigure 8-2 CD Pin Mechanism (OUT Pin Is Active High)
Note:

In the case of an Open Drain Active Low version, the VOUT signal will be high and transition to low state when the voltage on the VCD capacitor discharges to the set level based on the tCD timer.