Texas Instruments LM3444MM/S7002725

Overview

LM3444MM/S7002725 from Texas Instruments is a constant off-time AC/DC buck LED driver controller designed for offline solid-state lighting. It operates across 80–277 VAC input, delivers >1 A LED current, supports adaptive off-time programming via COFF pin, and integrates thermal shutdown and current limiting. It drives high-power LED strings in residential and commercial luminaires with passive PFC.

For engineers reviewing the LM3444MM/S7002725 datasheet, LM3444MM/S7002725 pinout, LM3444MM/S7002725 application, or LM3444MM/S7002725 equivalent, key selection criteria include its 10-pin VSSOP package, ISNS current-sense threshold (1.269 V typ), GATE drive capability (±0.77/0.88 A peak), COFF-based off-time programmability, and operation over –40°C to +125°C junction temperature.

Technical Context

The LM3444MM/S7002725 implements a proprietary adaptive constant off-time control architecture that maintains regulated LED current by dynamically adjusting switching frequency as VBUCK varies. Its valley-fill circuit interface enables passive power factor correction while supplying stable DC bus voltage to the buck stage.

It features dual current sensing: analog dimming via FILTER pin (750 mV reference), and overcurrent protection via ISNS pin (1.269 V threshold). The GATE output delivers ±0.77/0.88 A peak drive into MOSFET gate capacitance, with 15 ns rise/fall times under 1 nF load, enabling efficient high-frequency switching up to 1 MHz.

Key Specifications

Pinout & Package

LM3444MM/S7002725 is housed in a 10-pin VSSOP package (3.00 mm × 3.00 mm body size) with exposed thermal pad for enhanced power dissipation in compact LED drivers.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar AC/DC LED driver controller applications.

Compared with UCC28810DR and NCP1083DR2G, LM3444MM/S7002725 provides integrated gate drive, adaptive off-time ripple control, and dedicated analog/PWM dimming-making it optimal for high-current, flicker-sensitive, and thermally demanding LED lighting systems.

Availability

LM3444MM/S7002725 is available at Aetrix Electronics and suitable for residential lighting, commercial office fixtures, and industrial warehouse luminaires requiring stable component supply and long-term design continuity.

Supply support for LM3444MM/S7002725 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 for industrial, automotive, and lighting applications.

The LM3444 product line was engineered specifically for cost-effective, high-efficiency AC/DC LED drivers with passive PFC and flicker-free dimming-targeting solid-state lighting replacement of incandescent and fluorescent fixtures.

FAQ

What is the recommended minimum off-time setting for LM3444MM/S7002725 in high-line applications?

The LM3444MM/S7002725 minimum off-time is determined by the COFF pin RC network and must avoid violating the 200 ns minimum on-time limit. At maximum VBUCK (e.g., 380 VDC) and minimum VLED (e.g., 24 V), use Equation 12 from the datasheet to calculate tON(MIN); then select tOFF ≥ 1 µs to ensure stable CCM operation. Typical designs use 1–5 µs off-time for 50–200 kHz nominal fSW.

Can LM3444MM/S7002725 support 0–10 V analog dimming directly?

Yes, LM3444MM/S7002725 supports 0–10 V analog dimming via the FILTER pin, which accepts 0–750 mV DC input to linearly scale LED current. An external resistor divider (e.g., 10 kΩ + 100 kΩ) scales 0–10 V to 0–750 mV. No additional op-amp or level-shifting circuitry is required-the internal 750 mV reference and 1.12 MΩ input impedance enable direct interface.

What is the maximum LED string voltage supported by LM3444MM/S7002725?

LM3444MM/S7002725 does not impose a hard upper limit on VLED, but practical constraints arise from VBUCK headroom and MOSFET voltage rating. With VBUCK up to ~380 VDC (277 VAC × √2), and assuming 2–3 V MOSFET VDS(on), typical designs support up to 360 V LED string voltage. For 3 V/LED, this enables ~120 LEDs in series-verified in TI's typical application with 14-series LEDs at 24.5 V and scalable using same topology.

How does LM3444MM/S7002725 handle short-circuit conditions on the LED output?

Under LED short-circuit, LM3444MM/S7002725 detects >1.27 V on the ISNS pin via its I-LIM comparator, immediately disabling the GATE output and holding COFF low. A 180 µs restart timer prevents rapid cycling. This latched fault condition clears only after ISNS voltage drops below 1.174 V and COFF recovers-ensuring safe, non-destructive response to wiring faults or failed LED strings.

Is LM3444MM/S7002725 compatible with three-stage valley-fill PFC circuits?

Yes, LM3444MM/S7002725 is fully compatible with three-stage valley-fill PFC circuits. The datasheet explicitly states support for single-, two-, and three-stage configurations. In three-stage operation, diodes D5–D7 and capacitors C7–C9 form a series-parallel charge/discharge network that extends conduction angle and improves power factor beyond two-stage designs-validated in Figure 9 and Section 7.3.3 of SNVS682D.