Texas Instruments BQ27505YZGR-J4

Overview

BQ27505YZGR-J4 from Texas Instruments is a system-side Impedance Track™ fuel gauge IC for single-cell Li-ion battery packs, delivering ±1% state-of-charge (SOC) accuracy, real-time remaining capacity (mAh), time-to-empty (min), and state-of-health (%) via 400-kHz I²C interface. It integrates coulomb counting with 14-bit ADC resolution, internal temperature sensing, and 96 bytes of non-volatile flash for battery profile storage - deployed in smartphones, digital cameras, and handheld terminals.

For engineers reviewing the BQ27505YZGR-J4 datasheet, BQ27505YZGR-J4 pinout, BQ27505YZGR-J4 application, or BQ27505YZGR-J4 equivalent, key selection criteria include its NanoFree™ CSP-12 package (2.43 mm × 1.96 mm), ultra-low 4-μA hibernate current, support for 5–20 mΩ sense resistors, and dual-mode temperature sensing (internal or external NTC thermistor).

Technical Context

The BQ27505YZGR-J4 implements Texas Instruments' patented Impedance Track™ algorithm to model battery discharge curves and dynamically adjust for aging, self-discharge, and temperature/rate inefficiencies. It uses an integrating ADC with 14–15-bit resolution for coulomb counting and separate 14-bit ADCs for cell voltage (BAT) and thermistor (TS) measurements.

Power management includes five distinct modes - NORMAL (114 μA), SLEEP+ (58 μA), SLEEP (19 μA), HIBERNATE (4 μA), and BAT INSERT CHECK - automatically transitioned based on system events or host command. Communication occurs over I²C at up to 400 kHz with open-drain SDA/SCL, configurable interrupt outputs (SOC_INT, BAT_LOW, /BAT_GD), and 2.4–2.6 V supply operation.

Key Specifications

Pinout & Package

CSP-12 (NanoFree™) package: 12-ball, bottom-terminal chip-scale package measuring 2.43 mm × 1.96 mm with 0.5 mm ball pitch. Designed for minimal PCB footprint and low thermal resistance (θJA = 89°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with BQ27505YZGR-J4, BQ27426YZFT trades internal temperature sensing and ultra-low hibernate current for smaller size, while BQ27510-G3YZFT adds flash and algorithm enhancements at the cost of I²C speed and pin compatibility - making BQ27505YZGR-J4 optimal for cost-sensitive, single-cell, thermally demanding portable applications.

Availability

BQ27505YZGR-J4 is available at Aetrix Electronics and suitable for smartphone power management, digital camera battery monitoring, handheld terminal runtime optimization, MP3 player battery health tracking, and portable medical device fuel gauging requiring stable component supply and long-term lifecycle support.

Supply support for BQ27505YZGR-J4 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 technologies, with leadership in power management, signal chain, and battery management solutions.

The BQ27505YZGR-J4 belongs to TI's Impedance Track™ fuel gauge product line, engineered specifically for high-accuracy, low-power, system-side battery monitoring in space-constrained portable electronics.

FAQ

What is the primary function of the BQ27505YZGR-J4 in a battery management system?

The BQ27505YZGR-J4 serves as a system-side fuel gauge IC that provides real-time, high-accuracy battery metrics - including remaining capacity (mAh), state-of-charge (%), time-to-empty (min), and state-of-health (%) - for single-cell Li-ion batteries. It achieves this using TI's Impedance Track™ algorithm, integrated coulomb counting, and dual-path temperature sensing, all communicated over I²C to the host processor. The BQ27505YZGR-J4 does not control charging or protection; it reports battery status.

Does the BQ27505YZGR-J4 require an external sense resistor, and what value range is supported?

Yes, the BQ27505YZGR-J4 requires an external current-sense resistor connected between PACK– and system ground. It supports resistor values from 5 mΩ to 20 mΩ, with typical use at 10 mΩ. The device's integrating ADC features ±10 μV input offset and 14–15-bit resolution, enabling accurate coulomb counting without external amplification. The BQ27505YZGR-J4 measures differential voltage across SRP and SRN pins to compute charge flow.

Can the BQ27505YZGR-J4 operate with only its internal temperature sensor, or is an external thermistor mandatory?

The BQ27505YZGR-J4 can operate using only its internal temperature sensor for basic SOC estimation, but external thermistor support is optional and recommended for higher accuracy. The internal sensor covers –40°C to 85°C with –2 mV/°C gain, while the external TS pin accepts a 10 kΩ NTC (e.g., Semitec 103AT) for pack-level thermal monitoring. The BQ27505YZGR-J4 allows configuration to use either source - no external thermistor is mandatory unless application-level thermal fidelity demands it.

What power modes does the BQ27505YZGR-J4 support, and how low is its minimum quiescent current?

The BQ27505YZGR-J4 supports five power modes: NORMAL (114 μA), SLEEP+ (58 μA), SLEEP (19 μA), HIBERNATE (4 μA), and BAT INSERT CHECK. Its lowest operating current is 4 μA in HIBERNATE mode - achieved after entering SLEEP and issuing SET_HIBERNATE( ). This ultra-low current enables multi-year shelf-life preservation for battery-backed systems. Mode transitions occur automatically or via host I²C commands like Control( ) subcommands.

Is the BQ27505YZGR-J4 pin-compatible with other members of the bq275xx family, such as the BQ27510?

No, the BQ27505YZGR-J4 is not pin-compatible with the BQ27510 or BQ27520. While all share the CSP-12 package outline, pin assignments differ significantly - for example, the BQ27510 relocates TS and BI/TOUT functions and adds dedicated ALERT pin functionality. The BQ27505YZGR-J4 pinout is fixed per Table 2-1 in SLVSA40, and substitution requires PCB layout revision. Firmware and command sets also differ, precluding direct software compatibility.