Texas Instruments BQ27421YZFR-G1A

Overview

BQ27421YZFR-G1A from Texas Instruments is a single-cell Li-ion battery fuel gauge IC with integrated 7-mΩ sense resistor, Impedance Track™ algorithm, and I²C interface. It resides on the system board, powers directly from the battery via an internal 1.8-V LDO, and reports remaining capacity (mAh), state-of-charge (%), and battery voltage (mV) for embedded or removable packs.

For engineers reviewing the BQ27421YZFR-G1A datasheet, BQ27421YZFR-G1A pinout, BQ27421YZFR-G1A application, or BQ27421YZFR-G1A equivalent, key selection considerations include its 9-ball DSBGA package, 400-kHz I²C support, integrated coulomb counter with 16-bit resolution, ±0.1% voltage accuracy, and battery insertion detection via BIN pin.

Technical Context

The BQ27421YZFR-G1A implements Texas Instruments' patented Impedance Track™ algorithm to model cell impedance using real-time voltage, current, temperature, and open-circuit voltage data-enabling high-accuracy SOC estimation across aging, temperature, and load variations. Its integrated 7-mΩ sense resistor enables direct SRX-to-BAT current sensing without external components.

It operates in five power modes-NORMAL (93 µA), SLEEP (21 µA), HIBERNATE (9 µA), SHUTDOWN (0.6 µA), and INITIALIZATION-with automatic transitions and host-controlled entry/exit. The device uses an internal temperature sensor (±5°C accuracy) or accepts host-reported temperature, and supports both battery-insertion auto-detection and host-managed BAT_INSERT/BAT_REMOVE commands.

Key Specifications

Pinout & Package

Package: 9-ball NanoFree™ DSBGA (YZF), 1.62 mm × 1.58 mm, 0.5-mm pitch, bottom-side thermal pad not electrically connected.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BQ27421YZFR-G1A, the BQ27441YZFT-G1A offers identical functionality but targets a different Li-ion voltage profile, while the BQ27510-G3 adds flexibility at the cost of external components and larger footprint-making BQ27421YZFR-G1A optimal for space-constrained, single-cell, cost-sensitive consumer systems.

Availability

BQ27421YZFR-G1A is available at Aetrix Electronics and suitable for smartphones, tablets, and handheld terminals requiring stable component supply, long-term lifecycle support, and consistent firmware revision control.

Supply support for BQ27421YZFR-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 leadership in battery management ICs since 2005.

The BQ27421YZFR-G1A belongs to TI's Impedance Track™ fuel gauge product line, designed specifically for ultra-compact, low-power, system-side battery monitoring in portable consumer electronics where PCB space and bill-of-materials simplicity are critical.

FAQ

What is the function of the BIN pin on the BQ27421YZFR-G1A?

The BIN pin on the BQ27421YZFR-G1A is a battery insertion detection input that senses pack presence via logic level. When Operation Configuration bit [BIE] = 1 (default), a low signal indicates battery insertion; it requires a 10-kΩ pulldown on the pack and a 1.8-MΩ pullup on the system board. The BQ27421YZFR-G1A uses this signal to auto-initialize fuel gauging without host intervention, supporting both embedded and removable battery configurations.

Does the BQ27421YZFR-G1A require an external sense resistor?

No, the BQ27421YZFR-G1A does not require an external sense resistor-it integrates a precision 7-mΩ resistor between SRX and BAT pins. This eliminates layout sensitivity, reduces BOM count, and ensures consistent current measurement accuracy. The integrated resistor is rated for 2000 mA RMS continuous operation and supports up to 3500 mA peak pulses (250 ms), making the BQ27421YZFR-G1A suitable for high-current portable devices without external components.

How does the BQ27421YZFR-G1A achieve high-accuracy state-of-charge estimation?

The BQ27421YZFR-G1A achieves high-accuracy SOC estimation using Texas Instruments' Impedance Track™ algorithm, which dynamically models battery impedance based on real-time voltage, current, temperature, and open-circuit voltage measurements. It automatically compensates for aging, self-discharge, temperature gradients, and load-rate changes-delivering <2% SOC error over the battery's lifetime. The BQ27421YZFR-G1A also employs a 16-bit integrating ADC for coulomb counting and a 15-bit ADC for voltage measurement to ensure resolution fidelity.

What power modes does the BQ27421YZFR-G1A support, and how are they managed?

The BQ27421YZFR-G1A supports five power modes: INITIALIZATION, NORMAL (93 µA), SLEEP (21 µA), HIBERNATE (9 µA), and SHUTDOWN (0.6 µA). Transitions occur automatically based on I²C activity, GPOUT toggling, or timer events-but the host can force HIBERNATE or SHUTDOWN via Control() subcommands (SET_HIBERNATE, SHUTDOWN). In SHUTDOWN mode, the LDO is disabled and only GPOUT or I²C wake-up restores operation, enabling ultra-low standby power in always-on portable systems using the BQ27421YZFR-G1A.

Can the BQ27421YZFR-G1A be used with batteries other than LiCoO₂?

The BQ27421YZFR-G1A is factory-configured for LiCoO₂ chemistry (CHEM_ID 0x128, 4.2 V max), but supports other Li-ion variants via firmware reconfiguration. Valid alternatives include CHEM_ID 0x312 (4.35 V) and 0x3142 (4.4 V), accessible through DataFlash programming. However, successful adaptation requires matching the battery's OCV curve, charge profile, and aging behavior-TI recommends using the BQStudio tool and validated chem files. The BQ27421YZFR-G1A does not support LiFePO₄ or NiMH chemistries.