SLUSDY5 June   2022 BQ25172

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 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 Timing Requirements
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Device Power Up from Input Source
        1. 7.3.1.1 ISET Pin Detection
        2. 7.3.1.2 TMR Pin Detection
        3. 7.3.1.3 VSET Pin Detection
        4. 7.3.1.4 Charger Power Up
      2. 7.3.2 Battery Charging Features
        1. 7.3.2.1 NiMH Battery Charging Profile
        2. 7.3.2.2 Charging Safety Timers
        3. 7.3.2.3 Battery Cold, Hot Temperature Qualification (TS Pin)
      3. 7.3.3 Status Outputs (STAT)
        1. 7.3.3.1 Charging Status Indicator (STAT)
      4. 7.3.4 Protection Features
        1. 7.3.4.1 Input Overvoltage Protection (VIN OVP)
        2. 7.3.4.2 Output Overvoltage Protection (BAT OVP)
        3. 7.3.4.3 Output Overcurrent Protection (BAT OCP)
        4. 7.3.4.4 Thermal Regulation and Thermal Shutdown (TREG and TSHUT)
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown or Undervoltage Lockout (UVLO)
      2. 7.4.2 Sleep Mode
      3. 7.4.3 Active Mode
        1. 7.4.3.1 Standby Mode
      4. 7.4.4 Fault Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 NiMH Charger Design Example
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

7.1 Overview

The BQ25172 is an integrated 800-mA linear charger for 1-cell to 6-cell NiMH battery applications. The device has a single power output that charges the battery. When the system load is placed in parallel with the battery, the input current is shared between the system and the battery.

The device charges a NiMH battery in constant current mode only and terminates the charge cycle when the programmable timer, tSAFETY, expires or the battery voltage exceeds the VOUT_OVP threshold. An optional intermittent charging phase can be programmed to automatically recharge the NiMH battery for a reduced timer duration once its voltage falls below VRECHG.

The charger includes flexibility in programming of the charge current, charge safety timer duration, and series cell-count. This charger is designed to work with a standard USB connection or dedicated charging adapter (DC output).

The charger also comes with a full set of safety features: battery temperature monitoring, overvoltage protection, charge safety timer, and configuration pin (VSET, ISET, TMR) short and open protection. Upon application of a valid input power source, the configuration pins are checked for short and open circuits. All of these features and more are described in detail in the following sections.

The charger is designed for a single path from the input to the output to charge the battery. Once the input adapter has been connected, the charge current is applied and the safety timer is started. The charge current is programmed using the ISET pin. The safety timer is programmed by the TMR pin.

Power dissipation in the IC is greatest at high charge currents and low battery voltages. If the IC temperature reaches TREG, the IC enters thermal regulation, slows the timer clock by half, and reduces the charge current as needed to keep the temperature from rising any further.

Further details are described in Section 7.3.