Texas Instruments BQ27Z558YPHR

Overview

BQ27Z558YPHR from Texas Instruments is a flash-programmable, Impedance Track™ battery gas gauge IC for 1-series Li-ion/Li-polymer battery packs, featuring dual ADCs (coulomb counter + general-purpose), SHA-256 authentication, 1.2-V I²C support, and operation down to 2.0 V. It delivers ±1 µV typical input offset error in coulomb counting and supports high-side/low-side current sensing with 1-mΩ sense resistors - deployed in smartphones and portable health devices for precise remaining capacity and state-of-health estimation.

For engineers reviewing the BQ27Z558YPHR datasheet, BQ27Z558YPHR pinout, BQ27Z558YPHR application, or BQ27Z558YPHR equivalent, key selection considerations include its dual-ADC architecture enabling simultaneous current/voltage sampling, sub-3-µA hibernate mode current, 400-kHz I²C with 1.2-V logic compatibility, integrated 1.8-V LDO, and secure SHA-256 responder functionality for pack authentication.

Technical Context

The BQ27Z558YPHR implements a Harvard-architecture RISC CPU running up to 4.2 MHz with adaptive 3-stage pipeline and flash-based firmware (32 kB program, 4 kB data). Its coulomb counter uses a delta-sigma ADC with 3.74-µV resolution and <1-µV typical input offset error, while the second 16-bit delta-sigma ADC provides 38-µV resolution and auto-scaling full-scale range per channel.

It integrates two voltage references (REF1 = 1.21 V ±80 ppm/°C for CC/LDO; REF2 = 1.21 V ±20 ppm/°C for ADC), dual oscillators (LFO = 65.536 kHz, HFO = 16.78 MHz), and supports both I²C (100/400 kHz) and HDQ one-wire communication - with irreversible protocol selection at boot. The device operates from 2.0 V to 5.5 V and includes internal temperature sensing plus NTC thermistor biasing (18-kΩ pullup).

Key Specifications

Pinout & Package

Package: 12-pin DSBGA (YPH), 1.67 mm × 2.05 mm, 0.4-mm pitch, bottom-side thermal pad.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BQ27Z558YPHR, BQ27Z561YPHR offers incremental accuracy improvements in QMax convergence, while BQ28Z610RGER shifts focus to multi-cell scalability and safety certification - making BQ27Z558YPHR optimal for cost-sensitive, single-cell consumer applications demanding security and ultra-low quiescent current.

Availability

BQ27Z558YPHR is available at Aetrix Electronics and suitable for smartphones, portable health devices, and tablet computing applications requiring stable component supply, secure battery authentication, and long-term gauging accuracy.

Supply support for BQ27Z558YPHR 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 BQ27Z558YPHR belongs to TI's Impedance Track™ fuel gauge product line, designed specifically for high-accuracy, secure, and low-power single-cell Li-ion battery monitoring in space-constrained portable electronics.

FAQ

What is the primary function of the BQ27Z558YPHR in a battery management system?

The BQ27Z558YPHR serves as a standalone fuel gauge IC that accurately estimates remaining battery capacity, state of health, and state of charge using TI's Impedance Track™ algorithm. It performs real-time coulomb counting, voltage and temperature monitoring, and communicates results via I²C or HDQ to the host system - all while consuming less than 3 µA in hibernate mode. The BQ27Z558YPHR does not provide cell protection or charging control but feeds critical data to the system-level power manager.

Does the BQ27Z558YPHR support 1.2-V I²C logic levels, and why is this important?

Yes, the BQ27Z558YPHR supports 1.2-V I²C logic levels on SCL and SDA/HDQ pins, verified per datasheet Section 6.17. This enables direct interface with modern low-voltage application processors and SoCs without external level shifters - reducing BOM cost, PCB area, and signal integrity risk. The 400-kHz speed combined with 1.2-V compatibility makes the BQ27Z558YPHR ideal for high-density mobile designs where power efficiency and integration are critical.

How does the SHA-256 authentication feature work in the BQ27Z558YPHR?

The BQ27Z558YPHR implements a SHA-256 responder that authenticates the battery pack upon host request. The host sends a challenge; the BQ27Z558YPHR computes the HMAC-SHA-256 response using a secret key stored in secure flash memory. Only after successful authentication does the device unlock full register access - preventing counterfeit battery use and ensuring system-level safety. This feature is enabled via firmware configuration and requires no external crypto components. The BQ27Z558YPHR does not initiate authentication but responds securely to host queries.

Can the BQ27Z558YPHR operate below 2.5 V, and what is its minimum functional voltage?

Yes, the BQ27Z558YPHR is fully specified to operate down to 2.0 V (per Section 6.3 Recommended Operating Conditions), with guaranteed functionality including coulomb counting, ADC conversions, and I²C communication. Its low-voltage capability allows continuous battery monitoring even in deeply discharged states - critical for graceful system shutdown and accurate end-of-discharge characterization. Below 2.0 V, operation is not guaranteed; the device may enter reset or undefined behavior. The BQ27Z558YPHR maintains <11 µA sleep current across the full 2.0–5.5 V range.

What are the key differences between the BQ27Z558YPHR and the BQ27Z561YPHR?

The BQ27Z561YPHR shares identical pinout, package, and core architecture with the BQ27Z558YPHR but introduces an enhanced QMax update algorithm based on predicted OCV, improving full-charge capacity convergence speed by up to 3× after deep discharge. It also adds RSOC() charging compensation and refined JEITA sub-range handling. Both parts support SHA-256 and 1.2-V I²C, but BQ27Z561YPHR targets next-generation designs where faster learning and tighter SOC accuracy (<0.7%) are required. Firmware is not interchangeable; BQ27Z558YPHR cannot be upgraded to BQ27Z561YPHR functionality.