Texas Instruments BQ27545YZFT-G1

Overview

BQ27545YZFT-G1 from Texas Instruments is a single-cell Li-ion battery fuel gauge IC implementing Impedance Track™ technology for accurate state-of-charge (SOC), remaining capacity (mAh), time-to-empty (min), and voltage (mV) reporting. It integrates coulomb counting via 5–20 mΩ sense resistor, supports internal/external temperature sensing (NTC thermistor or on-die), and provides SHA-1/HMAC authentication for secure battery pack identification in space-constrained portable devices.

For engineers reviewing the BQ27545YZFT-G1 datasheet, BQ27545YZFT-G1 pinout, BQ27545YZFT-G1 application, or BQ27545YZFT-G1 equivalent, key selection considerations include its dual HDQ/I²C interface support, 15-ball DSBGA package (2.61 mm × 1.96 mm), low-power operating modes (down to 8 µA in HIBERNATE), integrated 2.5-V LDO regulator, and real-time detection of internal short and tab disconnection events.

Technical Context

The BQ27545YZFT-G1 uses a patented Impedance Track™ algorithm that models battery discharge curves by correlating cell impedance, open-circuit voltage (OCV), load current, and temperature - enabling <1% SOC error across lifetime and operating conditions. It performs continuous coulomb integration using a 14–15-bit integrating ADC on SRP/SRN inputs with ±10 µV offset and 1-s conversion time.

It features dual communication interfaces: HDQ (single-wire, 190–250 µs cycle time) and I²C (up to 400 kHz), both supporting Standard and Extended Commands for register/data flash access. Power management includes four autonomous modes - NORMAL (118 µA), SLEEP (62 µA), FULLSLEEP (23 µA), and HIBERNATE (8 µA) - triggered by activity or host command.

Key Specifications

Pinout & Package

Package: 15-ball Nano-Free™ DSBGA (YZF), 2.61 mm × 1.96 mm, 0.5-mm pitch, bottom-side solderable. Ideal for ultra-thin battery packs and embedded mainboard integration.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BQ27545YZFT-G1, BQ27542-G1 offers reduced feature set at lower cost but omits data logging, while BQ27546-G1 adds automotive-grade reliability and precision at higher BOM cost and firmware complexity.

Availability

BQ27545YZFT-G1 is available at Aetrix Electronics and suitable for smartphones, tablets, digital cameras, and handheld terminals requiring stable component supply, long-term lifecycle support, and validated battery authentication capability.

Supply support for BQ27545YZFT-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 leader specializing in analog, embedded processing, and power management technologies, with decades of expertise in battery management systems and precision analog ICs.

The BQ27545YZFT-G1 belongs to TI's bq27xxx fuel gauge family, engineered specifically for high-accuracy, low-power single-cell Li-ion battery monitoring in portable electronics where space, safety, and runtime predictability are critical.

FAQ

What communication interfaces does the BQ27545YZFT-G1 support?

The BQ27545YZFT-G1 supports both HDQ (single-wire, open-drain) and I²C (400 kHz, standard-mode) interfaces. It ships preconfigured in I²C mode but can be reconfigured to HDQ via firmware command. Both interfaces provide full access to registers and data flash, enabling flexibility in battery pack design and host system integration.

How does the BQ27545YZFT-G1 achieve <1% state-of-charge accuracy?

The BQ27545YZFT-G1 achieves <1% SOC accuracy using Texas Instruments' proprietary Impedance Track™ algorithm, which continuously models battery impedance, OCV, temperature, and load history. It combines 14–15-bit coulomb counting (SRP/SRN), 14–15-bit cell voltage (BAT) and thermistor (TS) ADCs, and on-the-fly Qmax adaptation - all validated across 500+ cycles and –40°C to +85°C.

What is the purpose of the SE pin on the BQ27545YZFT-G1?

The SE (Shutdown Enable) pin on the BQ27545YZFT-G1 is a push-pull output that signals the fuel gauge's active/shutdown state. When asserted, it indicates the device has entered SLEEP, FULLSLEEP, or HIBERNATE mode. System designers use this signal to coordinate host processor power states or disable auxiliary circuits during low-power operation of the BQ27545YZFT-G1.

Can the BQ27545YZFT-G1 operate without an external sense resistor?

No - the BQ27545YZFT-G1 requires an external 5 mΩ to 20 mΩ sense resistor between SRP and SRN to perform coulomb counting. The device does not support direct current sensing; removing the resistor disables fuel gauging functionality. Internal temperature sensing is optional, but external thermistor connection to TS is recommended for highest accuracy.

What authentication method does the BQ27545YZFT-G1 implement?

The BQ27545YZFT-G1 implements SHA-1/HMAC authentication using keys stored in its 64-byte data flash memory. This enables secure battery pack identification by verifying cryptographic signatures during host interrogation - preventing counterfeit or incompatible battery substitution in certified devices.