Texas Instruments BQ24400DG4

Overview

BQ24400DG4 from Texas Instruments is a programmable monolithic NiCd/NiMH fast-charge management IC with peak voltage (PVD), maximum temperature, and maximum charge time termination. It implements hysteretic current regulation via MOD pin control, supports pre-charge qualification below 950 mV, and delivers top-off at 1/16× fast-charge current for NiMH capacity optimization - used in multi-cell portable battery chargers.

For engineers reviewing the BQ24400DG4 datasheet, BQ24400DG4 pinout, BQ24400DG4 application, or BQ24400DG4 equivalent, key selection considerations include its 8-pin SOIC package, 4–6 V supply range, 2 V per-cell voltage limit, 0.225×VCC temperature cutoff threshold, and RC-programmable MTO timing for hold-off, top-off, and trickle intervals.

Technical Context

The BQ24400DG4 integrates a high-speed comparator, 3× voltage comparators, ADC, oscillator, and phase generator to execute a state-driven charge algorithm: charge qualification → battery conditioning → fast charge → optional top-off → trickle maintenance. It uses analog sensing at BAT (voltage), TS (NTC thermistor divider), and SNS (current-sense resistor) to enforce safety thresholds.

Its hysteretic switching controller drives the MOD pin to regulate charging current, with switching frequency tunable via external R_f/C_f filter (100–200 kHz typical). The RC pin serves dual roles: timer programming input and real-time state indicator (DC level = paused/inactive; sawtooth = active timing).

Key Specifications

Pinout & Package

Package: SOIC-8 (narrow-body, 150 mil width), also available in DIP-8 and TSSOP-8 - BQ24400DG4 specifically denotes the SOIC-8 variant with green molding compound and Pb-free finish.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar NiCd/NiMH charge management applications.

Compared with BQ24400DG4, BQ24401DG4 adds integrated bias regulation at minor cost premium, while MAX713CPA+ trades programmability for ruggedness and DIP compatibility - both require PCB layout review due to differing thermal pad and decoupling requirements.

Availability

BQ24400DG4 is available at Aetrix Electronics and suitable for portable power tools, medical handheld devices, two-way radio chargers, and emergency lighting systems requiring stable component supply across long-life product programs.

Supply support for BQ24400DG4 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 over 50 years of innovation in battery management solutions.

The BQ24400DG4 belongs to TI's dedicated nickel-chemistry charge controller product line, engineered for safe, high-efficiency fast charging of NiCd and NiMH battery packs in consumer, industrial, and medical equipment.

FAQ

What is the primary function of the BQ24400DG4 in a battery charging system?

The BQ24400DG4 serves as a fully autonomous NiCd/NiMH fast-charge management IC that executes a multi-stage algorithm: pre-qualification, trickle conditioning, constant-current fast charge, optional top-off, and maintenance trickle. It enforces safety limits via peak voltage (PVD), temperature (VTCO/VLTF), and time (MTO) - all programmable through external RC components. Its MOD pin directly controls the external pass element, making BQ24400DG4 the central decision engine in discrete charger topologies.

How does the BQ24400DG4 detect and respond to battery temperature faults?

The BQ24400DG4 monitors battery temperature via the TS pin using an NTC thermistor divider. It compares the sensed voltage against three thresholds: VTCO (0.225×VCC) for absolute cutoff, VHTF (0.25×VCC) for hot-fault suspension outside fast charge, and VLTF (0.5×VCC) for cold-fault suspension during fast charge/top-off. If V_TS < V_TCO, all charging stops immediately and LED goes high-Z. If V_TS > V_VLTF during fast charge, it suspends and enters trickle mode - ensuring BQ24400DG4 never applies high current outside safe thermal bounds.

Can the BQ24400DG4 be used with lithium-based batteries?

No, the BQ24400DG4 is explicitly designed for nickel-based chemistries (NiCd and NiMH) and must not be used with lithium-ion or lithium-polymer batteries. Its termination algorithms - peak voltage detection (PVD), -ΔV slope, and fixed 2.00 V/cell clamp - are incompatible with Li-ion's 4.2 V/cell requirement and CC/CV profile. Using BQ24400DG4 with lithium cells risks fire, explosion, or permanent damage due to uncontrolled overvoltage and lack of cell balancing. TI provides separate ICs like BQ2407x for Li-ion applications.

What external components are mandatory for basic BQ24400DG4 operation?

Four components are mandatory: (1) R_SNS sense resistor (sets fast-charge current via I = 0.05/R_SNS), (2) RC timing network (R_MTO + C_MTO for MTO calculation), (3) BAT resistive divider (RB1/RB2 scaling battery voltage to ≤2.00 V at pin), and (4) TS thermistor divider (NTC + fixed resistor generating V_TS). Additionally, VCC requires 10 µF + 0.1–0.22 µF decoupling, and SNS needs CHYS hysteresis capacitor - omission of any invalidates BQ24400DG4 safety-critical functions.

How does the BQ24400DG4 indicate charge status to the user?

The BQ24400DG4 uses its open-drain LED pin to communicate charge state: 1 Hz flashing indicates charge qualification or battery conditioning; steady low-level output means active fast charge; high-impedance (open) state signifies charge completion or sleep mode; and continuous high (if pulled up externally) occurs only during fault conditions like V_TS < V_TCO. No external logic is needed - the BQ24400DG4 drives standard LEDs directly through a series resistor, with behavior fully defined in Table 5 of the SLUS498A datasheet.