Texas Instruments BQ29401DCT3

Overview

BQ29401DCT3 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 quiescent current, and drives an external N-channel FET to blow a fuse during overvoltage events. It is used in notebook PCs and portable medical instrumentation as second-level safety protection.

For engineers reviewing the BQ29401DCT3 datasheet, BQ29401DCT3 pinout, BQ29401DCT3 application, or BQ29401DCT3 equivalent, key selection considerations include its fixed 4.45 V overvoltage threshold, 8-pin DCT (MSOP-8) package, CD pin-based delay timing, OUT pin open-drain output with 1.5–2.5 V high-level drive at –40 µA, and compatibility with multi-cell series configurations requiring redundant safety shutdown.

Technical Context

The BQ29401DCT3 implements a precision voltage comparator bank across up to four cell inputs (VC1–VC4), each referenced to an internal 4.45 V ±25 mV threshold. When any cell exceeds this level, a 0.2 µA current source charges an external capacitor on the CD pin until it reaches 1.2 V, triggering the OUT pin to activate.

Its architecture includes hysteresis of 300 mV to prevent chatter during recovery, supports stable operation under pulse charging, rejects supply ripple, and clamps CD to GND if all cells fall below V(PROTECT) before delay completion-ensuring full delay retention for subsequent events.

Key Specifications

Pinout & Package

Package: DCT (MSOP-8), 3.0 mm × 3.0 mm × 1.0 mm body, 0.65 mm pitch, RoHS-compliant, Pb-free CU SNBI finish, JEDEC MO-187 DA compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BQ29401DCT3, BQ29405DCT3 raises the protection threshold by 200 mV for specialized chemistries, while BQ29401PW retains identical functionality in a mechanically distinct TSSOP package-neither is pin-compatible nor electrically interchangeable without board revision.

Availability

BQ29401DCT3 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-lifecycle support.

Supply support for BQ29401DCT3 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, delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and personal electronics markets.

The BQ29401DCT3 belongs to TI's battery protection IC product line, designed specifically to provide robust, low-power, hardware-based secondary safety for multi-cell Li-ion battery packs in portable and mission-critical applications.

FAQ

What is the exact overvoltage protection threshold voltage of the BQ29401DCT3?

The BQ29401DCT3 has a fixed overvoltage protection threshold of 4.45 V ±25 mV per cell, as specified in the SLUS568C datasheet. This value is factory-trimmed and applies uniformly across all monitored cells (VC1–VC4). It is not user-adjustable and differs from other members of the bq2940x family such as the BQ29400 (4.35 V) or BQ29405 (4.65 V). The BQ29401DCT3 maintains this accuracy over the full operating temperature range of –25°C to +85°C.

How does the BQ29401DCT3 implement programmable delay timing?

The BQ29401DCT3 uses an internal 0.2 µA current source to charge an external capacitor connected to the CD pin. When the CD voltage reaches 1.2 V, the OUT pin activates. For a standard 0.22 µF capacitor, this yields a nominal delay of 1.32 seconds (t_D = 1.2 V × C_DELAY / 0.2 µA). The BQ29401DCT3 supports delay adjustment from ~1.0 s to ~2.0 s by varying C_DELAY, enabling designers to reject short-duration transients while ensuring timely response to sustained overvoltage.

Can the BQ29401DCT3 be used in 2-cell or 3-cell battery configurations?

Yes, the BQ29401DCT3 supports 2-, 3-, and 4-cell Li-ion configurations via specific terminal interconnections. In a 2-cell setup, VC1, VC2, and VC3 are tied together and connected to the top of the stack, while VC4 connects to the bottom cell's negative terminal. For 3-cell, VC1 and VC2 are shorted. These configurations are explicitly defined in the SLUS568C datasheet Figures 6 and 7, and the BQ29401DCT3's internal comparator bank automatically adapts to the reduced number of differential sense points.

What is the output drive capability of the BQ29401DCT3 OUT pin?

The BQ29401DCT3 OUT pin is an open-drain output capable of sinking up to 5 µA at 0.1 V (I_OL) and sourcing up to –1 mA at 3 V (I_OH). Its high-level voltage ranges from 1.5 V to 2.5 V when loaded with –40 µA, sufficient to drive the gate of a discrete N-channel MOSFET used to blow a fuse in the battery's positive rail. A pull-up resistor to VDD or another bias rail is required, as confirmed in the functional block diagram and Figure 1 of the BQ29401DCT3 datasheet.

Is the BQ29401DCT3 recommended for new designs?

No-the BQ29401DCT3 is marked "Not Recommended for New Designs" (NRND) in TI's official packaging addendum (2017), though it remains in production to support existing customers. TI recommends evaluating newer alternatives like the BQ77PL100 series for new battery protection architectures. However, the BQ29401DCT3 continues to be stocked and supported by Aetrix Electronics for legacy program continuity, with full traceable sourcing and lifecycle coordination available.