Texas Instruments BQ26500PW

Overview

BQ26500PW from Texas Instruments is a standalone single-cell Li-Ion/Li-Pol battery gas gauge IC that reports accurate state-of-charge (SoC), voltage (±20 mV), and temperature (±3 °K) without host processor calculations. It integrates coulometric current sensing via differential SRP/SRN inputs, features an internal time-base eliminating external crystals, and operates in four low-power modes - Active (<100 µA), Sleep (<2.5 µA), Ship (<1.7 µA), and Hibernate (<1.5 µA) - for portable electronics power management.

For engineers reviewing the BQ26500PW datasheet, BQ26500PW pinout, BQ26500PW application, or BQ26500PW equivalent, key selection considerations include its HDQ one-wire interface (5 kbits/s), auto-calibrating voltage-to-frequency converter (VFC) with <15 µV offset, EEPROM-programmable digital magnitude filter (DMF), and support for battery pack-level capacity learning across −20°C to 70°C operating range.

Technical Context

The BQ26500PW implements a fully differential, dynamically balanced voltage-to-frequency converter (VFC) for continuous charge/discharge integration, paired with an ADC for simultaneous battery voltage and die temperature measurement. All analog front-end paths feature automatic offset cancellation - no user calibration required.

It communicates over a bi-directional HDQ serial bus (5 kbits/s), uses internal registers for NAC, LMD, RSOC, ARTTE, and FLAGS, and supports EEPROM-based configuration of EDV thresholds, taper current, DMF, and temperature compensation constants. Power mode transitions (Active/Sleep/Ship/Hibernate) are controlled via MODE/CTRL registers and triggered by system events or host commands.

Key Specifications

Pinout & Package

Package: 8-pin TSSOP (PW), surface-mount, lead-free compatible, tape-and-reel packaging available with R suffix (e.g., BQ26500PWR).

Key Features

Applications

Equivalent & Alternatives

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

Compared with BQ26500PW, BQ27200YZFT offers I²C compatibility but increases interface complexity and power use, while BQ27425YZFT adds security and LED drive at the expense of Li-Pol support and fixed supply constraints - making BQ26500PW optimal for cost-sensitive, space-constrained, single-cell Li-Ion/Li-Pol packs requiring minimal interconnect and ultra-low ship-mode current.

Availability

BQ26500PW is available at Aetrix Electronics and suitable for smartphone battery packs, digital camera power systems, MP3 player runtime estimation, and PDA system-level power management requiring stable component supply across industrial temperature ranges and long-lifecycle production.

Supply support for BQ26500PW 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 headquartered in Dallas, Texas, specializing in analog, embedded processing, and power management technologies for industrial, automotive, and consumer markets.

The BQ26500PW belongs to TI's bqJUNIOR family of standalone battery gas gauge ICs, designed specifically for space-constrained portable applications requiring accurate, self-contained capacity monitoring without host processor dependency.

FAQ

What is the primary function of the BQ26500PW in a battery pack?

The BQ26500PW serves as a standalone fuel gauge IC that measures and reports battery state-of-charge (SoC), voltage, temperature, and time-to-empty without requiring host processor calculations. It performs coulometric integration using differential current sense inputs (SRP/SRN), applies temperature and discharge-rate compensation, and stores learned capacity (LMD) in RAM backed by RBI capacitor - enabling accurate SoC tracking across operating conditions in Li-Ion and Li-Pol battery packs.

Does the BQ26500PW require an external crystal oscillator?

No, the BQ26500PW does not require an external crystal oscillator. It incorporates an internal precision oscillator with ±2.5% frequency tolerance over −20°C to 70°C, which drives the voltage-to-frequency converter (VFC) and timing functions. This eliminates external timing components, reduces bill-of-materials cost, and simplifies PCB layout - a key advantage for compact portable battery pack designs.

How does the BQ26500PW handle battery capacity learning?

The BQ26500PW learns battery capacity during a full discharge cycle from full charge to the EDV1 threshold (≤6.25% remaining capacity), updating the Last Measured Discharge (LMD) register. Learning is validated only if no disqualifying events occur - such as cold temperature, light load, fast voltage drop, or excessive self-discharge. Once learned, LMD is retained in RAM and used to compute Nominal Available Capacity (NAC) and Relative State of Charge (RSOC), ensuring long-term accuracy without manual recalibration.

What communication interface does the BQ26500PW use, and what are its timing characteristics?

The BQ26500PW uses a bi-directional HDQ (High-Speed Data Queue) one-wire serial interface operating at 5 kbits/s. Its timing includes break detection (190 µs), host bit window (190 µs), and device response time (190–320 µs). The interface requires only one signal line plus ground, with internal HDQ pull-down enabling automatic Sleep mode entry when the host disconnects - reducing system-level power management complexity in portable devices.

Can the BQ26500PW operate directly from a single Li-Ion cell without regulation?

Yes, the BQ26500PW operates directly from a single Li-Ion or Li-Pol cell with supply voltage ranging from 2.6 V to 4.5 V. Its internal circuitry is optimized for this range, eliminating the need for an external LDO or DC-DC regulator. This direct connection simplifies battery pack design, improves power efficiency, and supports operation across the full usable voltage range of common 3.7 V nominal cells - from full charge (~4.2 V) down to end-of-discharge (~2.7 V).