Texas Instruments BQ27421YZFT-G1A

Overview

BQ27421YZFT-G1A from Texas Instruments is a system-side single-cell Li-ion fuel gauge IC with integrated 7-mΩ sense resistor, Impedance Track™ algorithm, and I²C interface. It resides on the host board, draws power directly from the battery via integrated LDO (1.8 V output), and reports remaining capacity (mAh), state-of-charge (%), voltage (mV), temperature (0.1°K), and state-of-health - enabling accurate battery management in space-constrained portable electronics.

For engineers reviewing the BQ27421YZFT-G1A datasheet, BQ27421YZFT-G1A pinout, BQ27421YZFT-G1A application, or BQ27421YZFT-G1A equivalent, key selection considerations include its 9-ball DSBGA package (1.62 mm × 1.58 mm), 400-kHz I²C support, ±0.1% voltage accuracy, integrated coulomb counter with 16-bit resolution, and battery insertion detection via BIN pin - all critical for smartphone, tablet, and handheld terminal design.

Technical Context

The BQ27421YZFT-G1A implements Texas Instruments' patented Impedance Track™ algorithm to model battery impedance, OCV, and load behavior across temperature (–40°C to 85°C) and aging - delivering high-accuracy SOC estimation without external calibration. Its integrated 7-mΩ sense resistor enables direct current measurement between PACK+ and VSYS, eliminating discrete shunt placement and layout complexity.

It operates in five power modes (NORMAL, SLEEP, HIBERNATE, SHUTDOWN, INITIALIZATION), achieving 9 µA hibernate and 0.6 µA shutdown current. Communication occurs over a 7-bit fixed I²C address (0x55), supporting standard and extended commands for real-time telemetry (e.g., StateOfCharge(), RemainingCapacity(), StateOfHealth()) and configuration (OpConfig(), CHEM_ID).

Key Specifications

Pinout & Package

Package: 9-ball NanoFree™ DSBGA (YZF), 1.62 mm × 1.58 mm, 0.5-mm pitch, bottom-side thermal pad (VSS at B2/C1).

Key Features

Applications

Equivalent & Alternatives

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

Compared with BQ27421YZFT-G1A, the YZFR-G1A variant offers identical form-factor and interface but restricts chemistry support, while the BQ27441YZFT-G1A delivers measurable improvements in thermal fidelity and current handling - making it suitable for next-generation high-drain portable systems where aging and temperature robustness are critical.

Availability

BQ27421YZFT-G1A is available at Aetrix Electronics and suitable for smartphones, tablets, and handheld terminals requiring stable component supply, long-term lifecycle support, and consistent performance across production batches.

Supply support for BQ27421YZFT-G1A 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, embedded processing, and power management technologies, with decades of leadership in battery management ICs.

The BQ27421YZFT-G1A belongs to TI's bq27xxx fuel gauge family, designed specifically for system-side, single-cell Li-ion battery monitoring in ultra-compact portable electronics - prioritizing minimal host firmware overhead and high accuracy without external components.

FAQ

What is the primary function of the BQ27421YZFT-G1A in a battery management system?

The BQ27421YZFT-G1A serves as a system-side fuel gauge IC that measures and reports real-time battery parameters - including remaining 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, the BQ27421YZFT-G1A resides on the host board and communicates via I²C, eliminating dependency on smart battery modules.

Does the BQ27421YZFT-G1A require an external sense resistor?

No, the BQ27421YZFT-G1A does not require an external sense resistor. It integrates a precision 7-mΩ (typical) sense resistor between the SRX and BAT pins, enabling direct current measurement without additional components. This integration reduces PCB area, eliminates trace resistance errors, and simplifies layout - a key advantage over discrete shunt-based solutions.

How does the BQ27421YZFT-G1A handle battery insertion detection for removable packs?

The BQ27421YZFT-G1A uses the BIN pin for battery insertion detection. For removable packs, a 10-kΩ pulldown resistor on the pack connects BIN to VSS, while the host board applies a 1.8-MΩ pullup to VDD. When the pack is inserted, BIN goes low, triggering detection if Operation Configuration bit [BIE] = 1 (default). The BQ27421YZFT-G1A then asserts the BAT_DET flag automatically.

What are the power consumption characteristics of the BQ27421YZFT-G1A in different operating modes?

The BQ27421YZFT-G1A features five low-power modes: NORMAL (93 µA), SLEEP (21 µA), HIBERNATE (9 µA), SHUTDOWN (0.6 µA), and INITIALIZATION. These modes are entered automatically based on activity or commanded via Control() subcommands (e.g., SET_HIBERNATE). The 0.6 µA shutdown current enables ultra-low standby power in always-on portable devices.

Can the BQ27421YZFT-G1A be used with batteries other than standard LiCoO₂?

Yes, the BQ27421YZFT-G1A supports multiple Li-ion chemistries through programmable CHEM_ID values. The BQ27421YZFT-G1A variant is configured for 4.3 V to 4.35 V LiCoO₂ (CHEM_ID = 0x312), but firmware can be adapted for other profiles - including 4.2 V (0x128) and 4.3 V to 4.4 V (0x3142) - via DataFlash programming using OpConfig() and BlockData() commands.