Texas Instruments BQ29400ADCT3R

Overview

BQ29400ADCT3R from Texas Instruments is a BiCMOS secondary overvoltage protection IC for 2-, 3-, or 4-cell Li-ion battery packs, featuring 4.40 V ±25 mV precision overvoltage detection, programmable delay via external capacitor on CD pin, <2 µA supply current, and integrated high-accuracy cell voltage monitoring across VC1–VC4 inputs. It drives an external N-channel FET to blow a fuse during overvoltage events in portable medical equipment.

For engineers reviewing the BQ29400ADCT3R datasheet, BQ29400ADCT3R pinout, BQ29400ADCT3R application, or BQ29400ADCT3R equivalent, this device supports second-level battery safety in space-constrained, low-power systems requiring stable threshold accuracy, ripple rejection during pulse charging, and reliable delay timing with 0.22 µF CD capacitance.

Technical Context

The BQ29400ADCT3R implements a precision comparator-based overvoltage detection architecture that independently monitors differential voltages between adjacent cell sense inputs (VC1–VC2, VC2–VC3, VC3–VC4, VC4–GND) against a trimmed internal reference. It initiates a controlled delay by sourcing 0.2 µA into an external capacitor at the CD pin upon threshold breach.

Upon CD pin voltage reaching 1.2 V, the OUT pin transitions high to activate an external fuse-blowing FET; recovery occurs only after all cells fall below V(PROTECT) – 300 mV hysteresis. The device operates across –25°C to 85°C with supply voltage up to 25 V and withstands input transients up to 28 V on all sense pins.

Key Specifications

Pinout & Package

Package: 8-pin DCT (MSOP-8), 3.0 mm × 3.0 mm × 1.0 mm body, RoHS-compliant, 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 BQ29400ADCT3R, BQ29401DCT3 offers a +50 mV threshold shift without layout change, whereas BD14000FVM sacrifices cell-count flexibility and delay programmability for lower unit cost in simpler systems.

Availability

BQ29400ADCT3R is available at Aetrix Electronics and suitable for portable medical devices, industrial handheld testers, and notebook PC battery packs requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for BQ29400ADCT3R 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 delivering analog, embedded processing, and connectivity solutions with emphasis on reliability, precision, and power efficiency.

The BQ29400ADCT3R belongs to TI's battery protection IC product line, designed specifically for hardware-enforced secondary safety in multi-cell Li-ion battery systems where firmware-independent fault containment is mandatory.

FAQ

What is the exact overvoltage detection threshold for BQ29400ADCT3R?

The BQ29400ADCT3R has a factory-trimmed overvoltage detection threshold of 4.40 V ±25 mV across the operating temperature range of –25°C to 85°C. This value is specified in the Electrical Characteristics table of the SLUS568C datasheet and applies to all cell voltage comparisons (VC1–VC2, VC2–VC3, VC3–VC4, VC4–GND). The BQ29400ADCT3R does not require external calibration or trimming to achieve this accuracy.

How is the delay time set for BQ29400ADCT3R, and what capacitor value yields ~1.5 seconds?

The BQ29400ADCT3R uses an internal 0.2 µA current source to charge an external capacitor connected to the CD pin; delay time is 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 per TI's design guidelines and Figure 2 in SLUS568C. The BQ29400ADCT3R's CD pin must be decoupled with a low-ESR ceramic capacitor placed close to the package.

Can BQ29400ADCT3R be used in a 2-cell Li-ion configuration, and how are the pins connected?

Yes, the BQ29400ADCT3R supports 2-cell configurations by connecting VC1, VC2, and VC3 together to the positive terminal of the top cell, VC4 to the junction between the two cells, and GND to the bottom cell's negative terminal. This configuration is explicitly shown in Figure 7 of the SLUS568C datasheet. The BQ29400ADCT3R automatically adapts its internal comparison logic without external programming.

Does BQ29400ADCT3R require external components beyond the CD capacitor?

The BQ29400ADCT3R requires only the CD timing capacitor and optionally input filter components: 100 Ω–1 kΩ resistors (RIN) and 0.01–0.1 µF capacitors (CIN) on each VCx pin for noise suppression, plus 0–1 kΩ resistor (RVD) and 0.1 µF capacitor (CVD) on VDD. No external voltage references, op-amps, or digital controllers are needed - the BQ29400ADCT3R functions as a complete analog protection subsystem.

Is BQ29400ADCT3R still recommended for new designs, and what is its lifecycle status?

No - Texas Instruments lists BQ29400ADCT3R as "Not Recommended for New Designs" (NRND) per the Package Option Addendum dated August 2017. It remains available for existing production but TI advises migration to newer alternatives like the BQ77PL100 family for new projects. Aetrix Electronics maintains inventory and provides continuity support for legacy BQ29400ADCT3R deployments.