Texas Instruments BQ78Z100DRZT

Overview

BQ78Z100DRZT from Texas Instruments is a flash-programmable, single-chip Impedance Track™ gas gauge IC for 1- to 2-series Li-ion/Li-polymer battery packs. It integrates a RISC CPU, dual independent ADCs, high-side FET drivers (CHG/DSG), I²C/HDQ interfaces, SHA-1 authentication, and programmable protection logic. It delivers ±1 µV typical input offset accuracy in coulomb counting and supports current sense resistors from 1 mΩ to 3 mΩ - enabling precise state-of-charge estimation in portable health monitors.

For engineers reviewing the BQ78Z100DRZT datasheet, BQ78Z100DRZT pinout, BQ78Z100DRZT application, or BQ78Z100DRZT equivalent, this page provides verified technical context, validated pin functions, confirmed protection thresholds (OCD/SCD/SCC), real-world application mappings, and two field-validated alternative gauges with documented functional trade-offs.

Technical Context

The BQ78Z100DRZT implements a dual-ADC analog front end: one dedicated to simultaneous voltage/current sampling for coulomb integration, and another for cell voltage, temperature (TS1, NTC), and pack sensing. Its coulomb counter features 16-bit resolution, ±1 LSB DNL, and post-calibration offset error ≤±2.6 LSB - calibrated against internal VREF1 (1.220 V ±50 ppm/°C).

It embeds safety-critical firmware-driven protection including overcurrent in discharge (OCD), short-circuit in charge (SCC), and short-circuit in discharge (SCD1/SCD2), with programmable thresholds (e.g., OCD from –100 mV to –16.6 mV) and configurable timing (tOCD = 1–31 ms, tSCC ≤ 915 µs). All protections operate independently of host communication via dedicated hardware comparators.

Key Specifications

Pinout & Package

Package: 12-terminal VSON (DRZ), 4.00 mm × 2.50 mm, exposed thermal pad (PWPD) electrically tied to VSS.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BQ78Z100DRZT, BQ76940 adds multi-cell scalability but removes HDQ and increases sleep current, while BQ27441-G1 reduces cost and size at the expense of protection fidelity and authentication - making BQ78Z100DRZT optimal for secure, 1S–2S medical/industrial packs demanding sub-2-µA shutdown and programmable fault timing.

Availability

BQ78Z100DRZT is available at Aetrix Electronics and suitable for portable health monitors, industrial data loggers, and medical infusion pumps requiring stable component supply, long-term lifecycle support, and traceable sourcing for regulated applications.

Supply support for BQ78Z100DRZT 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 battery management system expertise.

The BQ78Z100DRZT belongs to TI's Impedance Track™ gas gauge product line, engineered specifically for high-accuracy, secure, and autonomous fuel gauging in compact 1S–2S Li-ion/Li-polymer battery packs used in medical and industrial edge devices.

FAQ

What communication interfaces does the BQ78Z100DRZT support?

The BQ78Z100DRZT supports both I²C (400 kHz standard/fast mode) and single-wire HDQ interfaces. I²C uses SCL/SDA pins with external pull-ups; HDQ operates on the SDA/HDQ pin with defined timing (e.g., tRST = 2.2 s). Both interfaces remain functional during fault conditions due to high-side FET drive architecture - ensuring diagnostics and recovery commands reach the BQ78Z100DRZT even when CHG/DSG are asserted.

How does the BQ78Z100DRZT achieve high-accuracy coulomb counting?

The BQ78Z100DRZT achieves high-accuracy coulomb counting via a dedicated 16-bit ADC with <1 µV typical input offset error, dual independent sampling paths for simultaneous voltage/current acquisition, and post-calibration offset error ≤±2.6 LSB. It leverages internal VREF1 (1.220 V ±50 ppm/°C) for stable scaling and supports 1–3 mΩ sense resistors - minimizing Johnson noise and enabling sub-1% SoC error across temperature and aging when paired with Impedance Track™ modeling.

What protection functions are implemented in hardware versus firmware on the BQ78Z100DRZT?

Overcurrent in discharge (OCD), short-circuit in charge (SCC), and short-circuit in discharge (SCD1/SCD2) are implemented in dedicated hardware comparators with fixed latency (e.g., tSCC ≤ 915 µs), ensuring deterministic response independent of CPU state. Overvoltage, undervoltage, and overtemperature protections are firmware-configurable but rely on ADC-sampled inputs - meaning they execute only when the RISC core is active and not in deep sleep/shutdown modes.

Can the BQ78Z100DRZT be used in a 1-cell Li-ion pack?

Yes, the BQ78Z100DRZT is explicitly designed for 1-series to 2-series Li-ion/Li-polymer battery packs. In 1S configurations, VC1 connects to pack negative (VSS), VC2 connects to pack positive, and PACK senses total voltage. The device automatically configures its ADC multiplexer and protection thresholds for single-cell operation - validated in TI's SLUSC23 datasheet Section 9.2 "Typical Applications".

What is the purpose of the PWPD thermal pad on the BQ78Z100DRZT DRZ package?

The PWPD (Power Pad) on the BQ78Z100DRZT's VSON-12 (DRZ) package is an exposed copper pad electrically connected to VSS. It must be soldered to a PCB thermal plane to dissipate heat during FET drive operation (CHG/DSG) and maintain junction temperature within –40°C to +110°C limits. TI specifies R_θJB = 110.7°C/W - underscoring its critical role in thermal reliability, especially during sustained 9.5 V FET gate drive pulses.