Texas Instruments BQ29401PWR

Overview

BQ29401PWR from Texas Instruments is a BiCMOS secondary overvoltage protection IC for 2-, 3-, or 4-cell Li-ion battery packs. It provides precise cell voltage monitoring with ±25 mV accuracy at 4.45 V, programmable delay via external capacitor (0.22 µF typical), <2 µA supply current, and drives an external N-channel FET to blow a fuse during overvoltage events. It is used in notebook PCs and portable medical equipment as second-level safety protection.

For engineers reviewing the BQ29401PWR datasheet, BQ29401PWR pinout, BQ29401PWR application, or BQ29401PWR equivalent, this device serves as a dedicated secondary protector requiring accurate per-cell voltage sensing, stable delay timing under pulse charge, and high ripple rejection in compact battery management systems.

Technical Context

The BQ29401PWR implements a precision comparator-based overvoltage detection circuit that independently monitors up to four cell voltages (VC1–VC4) against a fixed 4.45 V ±25 mV internal reference. Each input channel features low input current (<0.3 µA) and operates across –0.3 V to 28 V, enabling direct connection to stacked Li-ion cells without level-shifting.

Upon overvoltage detection, a 0.2 µA internal current source charges an external capacitor on the CD pin; when CD reaches 1.2 V, the open-drain OUT pin pulls high to activate an external fuse-blowing FET. The device includes 300 mV hysteresis and automatically discharges CD if cell voltage falls below V(PROTECT) – Vhys before timeout.

Key Specifications

Pinout & Package

TSSOP-8 (PW) package, 3.0 mm × 4.4 mm × 1.2 mm max height, RoHS-compliant, green finish, moisture sensitivity level 1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BQ29401PWR, BQ29400PW offers earlier intervention at 4.35 V for conservative safety margins, while BQ29405DCT3 provides later cutoff at 4.65 V in a smaller MSOP package-both retain identical delay programming, low ICC, and 300 mV hysteresis but differ in trip voltage and physical form factor.

Availability

BQ29401PWR is available at Aetrix Electronics and suitable for notebook PC battery management, portable medical instrumentation, and industrial test equipment requiring stable component supply and long-term lifecycle support.

Supply support for BQ29401PWR 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 safety ICs.

The BQ2940x family was designed specifically for secondary overvoltage protection in multi-cell Li-ion battery packs, delivering precision, low power, and field-proven reliability in portable and medical applications.

FAQ

What is the exact overvoltage protection threshold voltage of the BQ29401PWR?

The BQ29401PWR has a fixed overvoltage detection threshold of 4.45 V ±25 mV across the operating temperature range of –25°C to 85°C. This value is factory-trimmed and does not require external calibration. It applies to each monitored cell voltage (VC1–VC4 relative to adjacent nodes), and the device triggers protection if any single cell exceeds this level. The BQ29401PWR's accuracy is confirmed in the SLUS568C datasheet Electrical Characteristics table under "Over voltage detection voltage".

How is the delay time set on the BQ29401PWR, and what capacitor value achieves a 1.5-second delay?

The BQ29401PWR uses an external capacitor on the CD pin to set overvoltage delay time, calculated as t_D = (1.2 V × C_DELAY) / 0.2 µA. For a 1.5-second delay, a 0.22 µF capacitor is recommended (yielding 1.0–2.0 s per datasheet). The BQ29401PWR's internal 0.2 µA current source charges CD until it reaches 1.2 V, then asserts OUT. This method ensures consistent timing independent of VDD variation.

Can the BQ29401PWR monitor fewer than four cells, and how are pins configured for 2-cell operation?

Yes, the BQ29401PWR supports 2-, 3-, or 4-cell configurations. For 2-cell operation, tie VC1, VC2, and VC3 together to the high-side terminal (e.g., pack+), connect VC4 to the junction between cells, and GND to pack–. This satisfies the required connection sequence (GND → VC4 → VC1=VC2=VC3) and ensures correct differential sensing. All unused VCx inputs must be connected-not left floating-as specified in the BQ29401PWR application diagrams.

What is the maximum continuous supply voltage the BQ29401PWR can tolerate on its VDD and VCx pins?

The BQ29401PWR supports a supply voltage range of –0.3 V to 28 V on both VDD and all VCx pins (VC1–VC4), per Absolute Maximum Ratings. This allows direct interfacing with stacked Li-ion batteries (up to 4S = ~16.8 V nominal) and accommodates transient overvoltages such as load dump or ESD. Operation above 25 V is outside recommended conditions but remains within safe absolute limits for short durations.

Is the BQ29401PWR still recommended for new designs, and what is its current status per Texas Instruments?

No-the BQ29401PWR is marked "Not Recommended for New Designs" (NRND) by Texas Instruments, as stated in the SLUS568C datasheet and TI's Packaging Addendum. It remains in production to support existing customers but TI advises migration to newer alternatives for new projects. The BQ29401PWR continues to be available through authorized distributors like Digi-Key and Mouser with full traceability and lifecycle coordination support from Aetrix Electronics.