Texas Instruments BQ27421YZFT-G1B

Overview

BQ27421YZFT-G1 from Texas Instruments is a system-side single-cell Li-ion battery fuel gauge IC with integrated 7-mΩ sense resistor, Impedance Track™ algorithm, and 1.8-V LDO regulator. It resides on the host board, supports embedded or removable batteries, and reports remaining capacity (mAh), state-of-charge (%), voltage (mV), temperature (0.1°K), and state-of-health. Used in space-constrained portable electronics requiring accurate runtime estimation.

For engineers reviewing the BQ27421YZFT-G1 datasheet, BQ27421YZFT-G1 pinout, BQ27421YZFT-G1 application, or BQ27421YZFT-G1 equivalent, key selection criteria include I²C interface compatibility (400 kHz), integrated coulomb counting with ±0.1% voltage accuracy and ±0.5% current accuracy over –40°C to 85°C, low-power operation (9 µA hibernate, 0.6 µA shutdown), and DSBGA-9 package footprint.

Technical Context

The BQ27421YZFT-G1 implements Texas Instruments' patented Impedance Track™ algorithm to model battery impedance, open-circuit voltage, and load behavior for high-accuracy state-of-charge prediction across aging, temperature, and discharge rate variations. It performs real-time coulomb counting using an integrated 7-mΩ sense resistor between BAT and SRX pins, with 16-bit effective resolution and 1-second conversion time.

It operates in five power modes-NORMAL (93 µA), SLEEP (21 µA), HIBERNATE (9 µA), SHUTDOWN (0.6 µA), and INITIALIZATION-with automatic transitions triggered by bus activity or internal events. Communication occurs via a fixed 7-bit I²C address (0x55) supporting standard and extended command sets for configuration, data read, and control functions including BAT_INSERT/BAT_REMOVE and GPOUT toggle.

Key Specifications

Pinout & Package

Package: DSBGA-9 (NanoFree™ chip-scale), 1.62 mm × 1.58 mm, 0.5-mm pitch, bottom-side ball layout.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fuel gauging applications.

Compared with BQ27421YZFT-G1, BQ27421YZFR-G1B offers chemistry-specific tuning for mid-voltage LiCoO₂ cells, while BQ27441YZFT-G1 delivers higher precision and extended diagnostics - both retain pin-to-pin compatibility and I²C command structure, enabling firmware reuse with minimal profile updates.

Availability

BQ27421YZFT-G1 is available at Aetrix Electronics and suitable for smartphones, tablets, and handheld terminals requiring stable component supply, long-term lifecycle support, and consistent gas-gauge performance across production batches.

Supply support for BQ27421YZFT-G1 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor company specializing in analog and embedded processing solutions, with leadership in power management, signal chain, and battery management technologies.

The BQ27421YZFT-G1 belongs to TI's bq27xxx fuel gauge family, designed specifically for compact, cost-sensitive portable electronics needing high-accuracy, low-power, system-side battery monitoring without external sense resistors or complex calibration.

FAQ

What is the primary function of the BQ27421YZFT-G1 in a battery management system?

The BQ27421YZFT-G1 serves as a system-side fuel gauge IC that accurately estimates remaining battery capacity (mAh), state-of-charge (%), voltage (mV), temperature (0.1°K), and state-of-health using its integrated 7-mΩ sense resistor and Impedance Track™ algorithm. Unlike pack-side gauges, it resides on the host PCB and interfaces directly with the system microcontroller via I²C - enabling real-time battery analytics without modifying the battery pack.

Does the BQ27421YZFT-G1 require an external sense resistor?

No, the BQ27421YZFT-G1 does not require an external sense resistor. It integrates a precision 7-mΩ (typical) high-side sense resistor between the BAT and SRX pins, eliminating the need for external current-sensing components, associated PCB routing, and calibration overhead. This integration reduces BOM cost, board area, and design complexity while maintaining ±0.5% current measurement accuracy.

What I²C address does the BQ27421YZFT-G1 use, and is it configurable?

The BQ27421YZFT-G1 uses a fixed 7-bit I²C slave address of 0x55 (0xAA write / 0xAB read). This address is hard-coded and not configurable via pins or registers. The device supports standard I²C operations including 1-byte write, quick read, incremental read/write, and repeated start - all compliant with FAST mode (400 kHz) timing specifications per the SLUSB85E datasheet.

How does the BQ27421YZFT-G1 handle battery temperature measurement?

The BQ27421YZFT-G1 includes an on-die temperature sensor delivering 0.1°K resolution measurements reported via the InternalTemperature() command (0x1E/0x1F). Alternatively, the host MCU can supply external temperature data using the Temperature() command (0x02/0x03). The Impedance Track™ algorithm automatically fuses either source with voltage and current data to maintain SOC accuracy across –40°C to 85°C without requiring external thermistors in most implementations.

What power-saving modes does the BQ27421YZFT-G1 support, and how are they entered?

The BQ27421YZFT-G1 supports five power modes: NORMAL (93 µA), SLEEP (21 µA), HIBERNATE (9 µA), SHUTDOWN (0.6 µA), and INITIALIZATION. Entry is automatic based on bus inactivity and internal timers, or manual via Control() subcommands (e.g., SET_HIBERNATE, SHUTDOWN). GPOUT toggling also wakes the device from SHUTDOWN. All modes preserve critical gas-gauge data in nonvolatile memory, ensuring resume accuracy without recalibration.