System-Side(tm) Fuel Gauge With Integrated Sense Resistor | Battery Gas Gauge - BQ27421-G1

BQ27421-G1 (ACTIVE)

System-Side(tm) Fuel Gauge With Integrated Sense Resistor | Battery Gas Gauge



The Texas Instruments bq27421-G1 fuel gauge is a minimally configured microcontroller peripheral that provides system-side fuel gauging for single-cell Li-Ion batteries. The device requires very little user configuration and system microcontroller firmware development.

The bq27421-G1 fuel gauge uses the patented Impedance TrackTM algorithm for fuel gauging, and provides information such as remaining battery capacity (mAh), state-of-charge (%), and battery voltage (mV).

Battery fuel gauging with the bq27421-G1 fuel gauge requires connections only to PACK+ (P+) and PACK– (P–) for a removable battery pack or embedded battery circuit. The tiny 9-ball, 1.62 mm × 1.58 mm, 0.5-mm pitch NanoFree™ chip scale package (DSBGA) is ideal for space-constrained applications.


  • Single-Cell Li-Ion Battery Fuel Gauge
    • Resides on System Board
    • Supports Embedded or Removable Batteries
    • Powered Directly from Battery with Integrated
    • Low-Value Integrated Sense Resistor
      (7 mΩ, Typical)
  • Easy-to-Configure Fuel Gauging Based on
    Patented Impedance Track™ Technology
    • Reports Remaining Capacity and State-of-
      Charge (SOC) with Smoothing Filter
    • Automatically Adjusts for Battery Aging, Self-
      Discharge, Temperature, and Rate Changes
    • Battery State-of-Health (Aging) Estimation
  • Microcontroller Peripheral Supports:
    • 400-kHz I2C Serial Interface
    • Configurable SOC Interrupt or
      Battery Low Digital Output Warning
    • Internal Temperature Sensor or
      Host-Reported Temperature

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Parametrics Compare all products in Battery Fuel Gauge

# Series Cells
Cell Chemistry
Battery Capacity (Max) (mAh)
Communication Interface
Battery Capacity (Min) (mAh)
External Capacity Indication
Gas Gauge Algorithm
Operating Temperature Range (C)
BQ27421-G1 BQ27425-G2A BQ27425-G2B
Single Cell      Single Cell   
Li-Ion/Li-Polymer    Li-Ion/Li-Polymer    Li-Ion/Li-Polymer   
8000    4000    4000   
I2C    I2C    I2C   
100    100    100   
None    None    None   
System    System    System   
IT (High accuracy)    IT (High accuracy)    IT (High accuracy)   
-40 to 85    -40 to 85    -40 to 85