Texas Instruments BQ26221PW

Overview

BQ26221PW from Texas Instruments is a single-wire HDQ battery monitor 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 delivers state-of-charge estimation in portable electronics with 30 µA operating current and 600 nA hibernate mode.

For engineers reviewing the BQ26221PW datasheet, BQ26221PW pinout, BQ26221PW application, or BQ26221PW equivalent, key selection considerations include HDQ interface timing compliance (5 kbit/s), VFC-based coulometric integration (3.0 µVH resolution), BAT voltage sensing range (2.6–4.5 V), TSSOP-8 package thermal performance, and register-level self-discharge compensation logic.

Technical Context

The BQ26221PW implements a voltage-to-frequency converter (VFC) architecture for high-accuracy charge/discharge current integration, with automatic offset compensation eliminating host calibration. Its internal precision oscillator replaces external crystals, enabling system-level timing independence.

It uses a register-mapped HDQ command protocol (asynchronous return-to-one, LSB-first) to access 122-byte memory space: 8-byte ID ROM (including LSB gain correction), 32-byte RAM shadowed by flash, 64-byte user flash, and 18 special-function registers - all accessible without interrupt or polling overhead on the host side.

Key Specifications

Pinout & Package

TSSOP-8 package (PW suffix), 3.0 mm × 4.4 mm body, 0.65 mm pitch, exposed pad optional. RoHS-compliant, tape-and-reel delivery (PWR variant).

Key Features

Applications

Equivalent & Alternatives

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

Compared with BQ26221PW, BQ27220YZFT shifts computation burden to the IC but loses RBI-backed RAM retention, while MAX17048 offers superior SoC modeling at the cost of added BOM and reduced ultra-low-power capability below 1 µA.

Availability

BQ26221PW is available at Aetrix Electronics and suitable for smartphone battery management, tablet power monitoring, wearable health tracker design, Bluetooth headset fuel gauge implementation, and portable medical device power supervision requiring stable component supply and long-term lifecycle support.

Supply support for BQ26221PW 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 experience in battery management solutions.

The BQ26221PW belongs to TI's battery monitor IC product line, engineered specifically for HDQ-based, low-pin-count, single-cell Li-ion/Li-polymer pack integration in space-constrained portable devices.

FAQ

What is the primary function of the BQ26221PW in a battery pack?

The BQ26221PW serves as a coulometric battery monitor IC that measures battery voltage (via BAT pin), temperature (via internal sensor), and charge/discharge current (via SRP/SRN differential inputs) to enable host-based state-of-charge calculation. It integrates all required analog front-end functions-including VFC-based current integration, 11-bit ADC, and precision oscillator-into a single TSSOP-8 device, eliminating external components like crystals or thermistors. The BQ26221PW communicates results over HDQ to the host controller for final fuel-gauge processing.

How does the BQ26221PW handle voltage and temperature calibration?

The BQ26221PW stores factory-trimmed calibration data in its 8-byte ID ROM, including LSB gain correction factor (at address 0x79) and voltage ADC offset bits (in BATH register bits 3–7). Host firmware must apply these values using the formula: Correct VBAT = VBAT × (2.44 + LSB correction factor) − offset. Temperature calibration is handled internally-the die temperature is reported directly in Kelvin via TMPH/TMPL registers with ±4 K accuracy across −20°C to 70°C, requiring no host calibration.

What are the power states supported by the BQ26221PW and their current consumption?

The BQ26221PW supports three defined power states: Operating mode draws 30 µA typical (up to 37 µA) at 4.3 V; Sleep mode reduces current to 1 µA typical (up to 5 µA) while retaining SCR updates; Hibernate mode activates when VCC drops below 1.9–2.45 V POR threshold, drawing only 600 nA from the RBI pin to preserve RAM contents. All transitions are controlled via HDQ commands or supply conditions-no external wake-up signal is needed, as HDQ edge detection triggers exit from Sleep/Hibernate.

Can the BQ26221PW be used with multi-cell battery configurations?

The BQ26221PW is designed explicitly for single-cell Li-ion or Li-polymer battery packs, as confirmed by its BAT pin voltage range (2.6–4.5 V), internal reference optimization, and typical application circuit (Figure 3) showing direct connection to a single cell. It does not support cell balancing, high-side sensing, or stacked voltage monitoring. For multi-cell applications, TI recommends dedicated multi-cell monitors such as the BQ769x2 series. Using BQ26221PW in multi-cell configurations would require external level-shifting or isolation, violating its specified operating conditions and voiding accuracy guarantees.

What memory resources does the BQ26221PW provide for battery data storage?

The BQ26221PW provides 122 bytes of structured memory: 8 bytes of factory-programmed ID ROM (including device code and gain correction), 32 bytes of flash-backed RAM (retained during Sleep/Hibernate via RBI), 64 bytes of general-purpose flash (organized in three 32-byte pages), and 18 special-function registers (for counters, mode control, and configuration). Flash endurance is rated at 10,000 write cycles, and page-level erase/program operations are executed via the FCMD register using documented command codes (e.g., 0x45 for RAM-to-flash transfer). This architecture enables persistent storage of battery chemistry, serial number, manufacturing date, and runtime history without external EEPROM.