SLUSDK0A August   2020  – March 2021 BQ25171-Q1


  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  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. 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. ISET Pin Detection
        2. CHM_TMR Pin Detection
        3. VSET Pin Detection
        4. Charger Power Up
      2. 7.3.2 Battery Charging Features
        1. Lithium-Ion Battery Charging Profile
          1. NiMH Battery Charging Profile
        2. Charge Termination and Battery Recharge
        3. Charging Safety Timers
        4. Battery Cold, Hot Temperature Qualification (TS Pin)
      3. 7.3.3 Status Outputs (STAT1, STAT2)
        1. Charging Status Indicator (STAT1, STAT2)
      4. 7.3.4 Protection Features
        1. Input Overvoltage Protection (VIN OVP)
        2. Output Overvoltage Protection (BAT OVP)
        3. Output Overcurrent Protection (BAT OCP)
        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. Standby Mode
      4. 7.4.4 Fault Mode
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 1s LiFePO4 Charger Design Example
        1. Design Requirements
        2. Detailed Design Procedure
          1. Program the Fast Charge Current, ISET:
          2. TS Function
        3. Application Curves
      2. 8.2.2 2s Li-Ion Charger with Power Path Design Example
        1. Design Requirements
      3. 8.2.3 4s NiMH Charger Design Example
        1. Design Requirements
  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
NiMH Battery Charging Profile

The device charges a NiMH battery in two phases: constant current and intermittent charge (optional). The duration for constant current charing is controlled by the charge timer, which is programmed using the CHM_TMR pin. Intermittent charging is designed to replenish the natural self-discharge of NiMH by restarting a short charge cycle (25% of programmed charge timer) when the output voltage falls below VRECHG threshold. If the intermittent charging function is disabled, the device will charge a battery once, and not start a recharge cycle automatically. In this case, a new charge cycle can be initiated by toggling the input supply or the CE pin.

Before initiating a NiMH charge cycle, the device checks for a full battery. If battery voltage is above VRECHG, the battery is considered full and the device does not charge. Once the battery voltage falls below VRECHG, the device automatically begins charging. If the intermittent charging function is disabled, a single charge cycle is initiated with the charge timer as programmed by CHM_TMR pin. If intermittent charging is enabled, an intermittent charge cycle is initiated with charge timer as 25% of CHM_TMR programmed value.

If the charger is in thermal regulation during charging, the actual charging current will be less than the programmed value. For NiMH charging, termination by timer is still enabled, but the charging safety timer is counted at half the clock rate. For more information, refer to Section

GUID-20210308-CA0I-WVRB-BJG3-LZPVCSVZVG9W-low.svg Figure 7-4 NiMH Battery Charging Profile with Intermittent Charging Disabled
GUID-20210308-CA0I-MW1Z-BFG3-5LZHFGBH6SMJ-low.svg Figure 7-5 NiMH Battery Charging Profile with Intermittent Charging Enabled