SLUSFQ8B December   2024  – June 2025 BQ2969T

PRODMIX  

  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
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Pin Details
        1. 7.3.1.1 Input Sense Voltage, Vx
        2. 7.3.1.2 Output Drive, OUT
        3. 7.3.1.3 Supply Input, VDD
        4. 7.3.1.4 Control / PTC Input Pin, CTL
        5. 7.3.1.5 Regulated Supply Output, REG
      2. 7.3.2 Overvoltage Sensing for OUT
      3. 7.3.3 Regulator Output Voltage
    4. 7.4 Device Functional Modes
      1. 7.4.1 NORMAL Mode
      2. 7.4.2 OVERVOLTAGE Mode
      3. 7.4.3 UNDERVOLTAGE Mode
      4. 7.4.4 CTL / OVERTEMPERATURE Mode
      5. 7.4.5 CUSTOMER TEST 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 Curves
      4. 8.2.4 CTL for PTC Thermistor Protection
      5. 8.2.5 CTL for External OUT Overdrive
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Third-Party Products Disclaimer
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Support Resources
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

8.2.4 CTL for PTC Thermistor Protection

The CTL pin of the BQ2969T family can provide overtemperature (OT) protections when a PTC thermistor is attached between the CTL and VDD pins of the device. The CTL pin has a factory programmable internal pulldown resistance (RPD) with 500kΩ, 1MΩ, 2MΩ, and 10MΩ options. In all operational modes RPD is pulsed at a low duty cycle, making a higher effective resistance of RPD, to avoid drawing significant additional current from the supply.

BQ2969T BQ2969T PTC Configuration Reference SchematicFigure 8-8 BQ2969T PTC Configuration Reference Schematic

The overtemperature mode is entered when the voltage of the CTL pin falls below the VDD - VCTL threshold for tUVDELAY, in this mode the OUT pin is then asserted. The OUT pin is typically used to then enable an external FET and blow the fuse to disable the pack. Figure 8-9 shows an example of CTL being used for overtemperature protection. The OT voltage trip threshold is defined as the voltage VDD minus VCTL. For example assume a VDD of 16V and typical VCTL of 2.8V, to calculate the OT voltage trip threshold, 2.8V is subtracted from 16V, which provides a nominal OT trip voltage threshold of 13.2V. The voltage across the PTC is nominally always VCTL, when the OT voltage trip threshold is met.

Overtemperature hysteresis is implemented with the RPDH resistance. After the overtemperature protection triggers, the RPD resistance halves, for example if using the 10MΩ option, the new resistance (RPDH) is now 5MΩ. The new lower resistance means that to recover from an overtemperature condition a lower resistance from the PTC is needed, to cause the CTL pin voltage to rise above the OT voltage trip threshold. When the temperature drops, the PTC resistance lowers to allow OT recovery as the CTL pin voltage again increases in voltage.

BQ2969T Overtemperature protection Figure 8-9 Overtemperature protection