Texas Instruments BQ26221PWR

Overview

BQ26221PWR from Texas Instruments is a single-wire HDQ battery gas gauge IC for Li-ion/Li-polymer packs, integrating 11-bit ADC (2.44 mV LSB), differential current sensing (±100 mV input range), internal temperature sensor (±4 K accuracy), 32-byte flash-backed RAM, and 96-byte flash memory. It operates from 2.8 V to 4.5 V and delivers 30 µA operating current in portable power management systems.

For engineers reviewing the BQ26221PWR datasheet, BQ26221PWR pinout, BQ26221PWR application, or BQ26221PWR equivalent, this page provides verified technical context, validated pin functions, confirmed low-power modes (1 µA sleep, 600 nA hibernate), real-world register-mapped HDQ interface timing, and alternative options with documented functional alignment for battery fuel gauging in handheld electronics.

Technical Context

The BQ26221PWR implements a voltage-to-frequency converter (VFC) architecture for coulometric charge/discharge integration with automatic offset compensation, enabling accurate capacity tracking without host calibration. Its autocalibrating VFC achieves ±0.2% INL and gain stability of ±0.5%/V over supply and ±0.005%/°C over temperature.

It uses a register-mapped HDQ protocol (5 kbit/s, asynchronous return-to-one) with break-based synchronization, supporting read/write access to 122-byte memory space - including 8-byte ID ROM (with factory LSB gain correction), 32-byte RAM, 64-byte user flash, and 18 special-function registers - all accessible via single-wire bidirectional communication.

Key Specifications

Pinout & Package

Package: TSSOP-8 (PW), 3.0 mm × 4.4 mm, 0.65 mm pitch, tape-and-reel (R suffix).

Key Features

Applications

Equivalent & Alternatives

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

Compared with BQ26221PWR, BQ26200PWR reduces system BOM cost by eliminating internal temperature sensing but increases design complexity with external component requirements; BQ27220YZFT shifts to I²C and adds protection features at the expense of footprint and interface compatibility - making BQ26221PWR optimal for HDQ-based OMAP platforms requiring proven, low-risk integration.

Availability

BQ26221PWR is available at Aetrix Electronics and suitable for smartphone battery packs, PDA power management systems, and portable medical monitor designs requiring stable component supply, long-lifecycle support, and TI-qualified gas gauge performance.

Supply support for BQ26221PWR 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 over 50 years of innovation in battery management ICs.

The BQ26221PWR belongs to TI's bq26xxx gas gauge family, engineered specifically for single-cell Li-ion/Li-polymer applications in space-constrained portable electronics where HDQ simplicity, ultra-low power, and factory-traceable calibration are essential.

FAQ

What is the primary function of the BQ26221PWR in a battery system?

The BQ26221PWR serves as a standalone fuel gauge IC that measures battery voltage, temperature, and charge/discharge current via differential sensing to compute state-of-charge (SOC) and track capacity degradation. It communicates results to the host processor through the HDQ interface and retains critical data in flash-backed RAM during power loss. The BQ26221PWR does not include protection or charging functions - it is strictly a monitoring device.

Does the BQ26221PWR require an external crystal oscillator?

No, the BQ26221PWR incorporates a high-accuracy internal timebase that eliminates the need for an external crystal oscillator. This integrated precision oscillator supports all timing-critical functions including coulometric integration, self-discharge counting, and HDQ communication synchronization. The BQ26221PWR achieves stable operation across −20°C to 70°C without external timing components, reducing bill-of-materials and PCB area.

How does the BQ26221PWR handle battery voltage measurement accuracy?

The BQ26221PWR uses an 11-bit ADC with 2.44 mV LSB resolution to measure battery voltage at the BAT pin. Factory-programmed gain correction (stored in ID ROM byte 0x79) and offset data (in BATH register bits 3–7) enable host-side correction of raw readings. The BQ26221PWR supports full-scale 0–5 V input, optimized for 3.0–4.2 V Li-ion cells, and delivers corrected voltage accuracy within ±15 mV after applying both corrections per the datasheet formula.

Can the BQ26221PWR operate from a single Li-ion cell without regulation?

Yes, the BQ26221PWR operates directly from a single Li-ion or Li-polymer cell across its full usable voltage range of 2.8 V to 4.5 V. Its internal circuitry is designed for unregulated battery input, and the device enters hibernate mode below 1.9 V (POR threshold), drawing only 600 nA from the RBI pin to preserve RAM contents. This enables seamless integration into compact battery packs without additional voltage regulation circuitry.

What memory resources are available on the BQ26221PWR for storing battery-specific data?

The BQ26221PWR provides 96 bytes of nonvolatile memory: 8 bytes of factory-programmed ID ROM (including device code and ADC gain correction), 32 bytes of flash-backed RAM (retained across power cycles), and 64 bytes of general-purpose user flash. These resources store calibrated parameters, battery chemistry identifiers, manufacturing dates, and usage logs. The BQ26221PWR supports page erase and byte programming via HDQ commands, with 10,000 write cycles and 5-year data retention guaranteed.