Texas Instruments BQ29449DRBT

Overview

BQ29449DRBT from Texas Instruments is a second-level overvoltage protection IC for 2-, 3-, or 4-series Li-ion battery packs, featuring ±25 mV overvoltage detection accuracy (0°C to 60°C), 4.30 V fixed OVP threshold, <2 µA typical supply current, and external capacitor-controlled delay timing. It operates across –40°C to +110°C and drives an open-drain OUT signal to disconnect protection circuitry in notebook computers and power tools.

For engineers reviewing the BQ29449DRBT datasheet, BQ29449DRBT pinout, BQ29449DRBT application, or BQ29449DRBT equivalent, key selection factors include its 4.30 V precision OVP threshold, DRB 8-pin QFN package with exposed thermal pad, non-latching output behavior, and compatibility with multi-cell voltage monitoring topologies requiring low-quiescent-current secondary protection.

Technical Context

The BQ29449DRBT implements independent cell voltage monitoring via four VCx inputs (VC1–VC4) referenced to GND, comparing each against an internal 4.30 V reference with ±25 mV accuracy over 0°C–60°C. An internal 140 nA current source charges the external CD capacitor during overvoltage events, triggering OUT high after delay time td = CCD × xDELAY (nominally 9.0 s/µF).

No latch function is implemented - the OUT pin returns low when overvoltage clears and the CD capacitor discharges fully. The device supports Customer Test Mode (CTM) at VDD ≈ VC1 + 9.5 V, reducing delay scale factor to 0.08 s/µF for accelerated production testing, with no impact on normal operation.

Key Specifications

Pinout & Package

Package: DRB - 8-pin 3.0 mm × 3.0 mm SON (Small Outline No-Lead) with exposed thermal pad, RoHS-compliant, MSL Level-2-260°C-1 year.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar secondary overvoltage protection applications.

Compared with BQ29449DRBT, BQ29441DRBT offers identical functionality at a higher 4.40 V threshold for advanced Li-ion variants, while BD14000GUL provides ultra-compact 2S/3S protection but omits 4S capability and uses a different package - making BQ29449DRBT optimal for cost-sensitive, thermally demanding 4-series applications requiring 4.30 V precision.

Availability

BQ29449DRBT is available at Aetrix Electronics and suitable for notebook computers, power tools, and portable medical devices requiring stable component supply with guaranteed long-term sourcing and full traceability.

Supply support for BQ29449DRBT 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, embedded processing, and power management technologies, with leadership in battery management solutions.

The bq2944x product line delivers secondary overvoltage protection for multi-cell Li-ion battery packs, targeting applications where safety redundancy, low power consumption, and precision voltage thresholds are critical.

FAQ

What is the overvoltage protection threshold of the BQ29449DRBT?

The BQ29449DRBT has a fixed overvoltage protection (OVP) threshold of 4.30 V. This value is factory-trimmed and specified with ±25 mV accuracy over 0°C to 60°C ambient temperature. It applies uniformly to all monitored cells (VC1–VC2, VC2–VC3, VC3–VC4, and VC4–GND), enabling consistent secondary protection across 2-, 3-, or 4-series Li-ion configurations without external components.

Does the BQ29449DRBT include a latch function on the OUT pin?

No, the BQ29449DRBT does not include a latch function. Its OUT pin is non-latching: it transitions high after the CD capacitor charges to ~1.2 V (triggered by internal 140 nA current source), but returns low automatically once the overvoltage condition clears and the CD capacitor fully discharges. This behavior distinguishes it from latched variants like BQ2944L9 and supports self-recovering protection schemes.

How is the overvoltage delay time set for the BQ29449DRBT?

The overvoltage delay time for the BQ29449DRBT is set using an external capacitor connected to the CD pin. Delay time (td) equals CCD × xDELAY, where xDELAY is nominally 9.0 s/µF. For example, a 0.33 µF capacitor yields ~3 seconds delay. The internal 140 nA current source charges CCD until it reaches ~1.2 V, at which point OUT asserts high - providing precise, user-adjustable response timing without trimming resistors.

What package type and thermal characteristics does the BQ29449DRBT use?

The BQ29449DRBT uses the DRB package: an 8-pin 3.0 mm × 3.0 mm SON (Small Outline No-Lead) with exposed thermal pad. Its junction-to-ambient thermal resistance (θJA) is 50.5°C/W on a JEDEC-standard high-K board. The exposed pad must be soldered to PCB copper for optimal thermal and mechanical performance, as specified in TI's SLUA271 layout guidelines.

Can the BQ29449DRBT monitor 4-series Li-ion battery packs?

Yes, the BQ29449DRBT fully supports 4-series Li-ion battery packs using all four VCx inputs: VC1 (top cell), VC2 (second cell), VC3 (third cell), and VC4 (bottom cell referenced to GND). The device compares each inter-cell voltage (VC1–VC2, VC2–VC3, VC3–VC4, VC4–GND) independently against the 4.30 V threshold, making it suitable for quad-cell configurations in power tools and industrial equipment.