Texas Instruments LM3404MR/NOPB

Overview

LM3404MR/NOPB from Texas Instruments is a monolithic 1-A constant-current buck regulator IC designed for driving high-power LED arrays in automotive and industrial lighting systems. It integrates a high-side N-channel MOSFET (R_DS(on) = 0.75 Ω typ), operates from 6 V to 42 V input, delivers up to 1.2 A output current, features cycle-by-cycle current limiting, and supports PWM dimming via the DIM pin.

For engineers reviewing the LM3404MR/NOPB datasheet, LM3404MR/NOPB pinout, LM3404MR/NOPB application, or LM3404MR/NOPB equivalent, key selection considerations include its hysteretic controlled-on-time (COT) architecture, 200-mV current-sense reference voltage, SO PowerPAD-8 package thermal performance (R_θJA = 44.7 °C/W), and compatibility with ceramic-only or capacitor-less output configurations.

Technical Context

The LM3404MR/NOPB implements a controlled-on-time (COT) buck topology with hysteretic feedback control, eliminating need for external loop compensation. Its on-time is programmable via R_ON and inversely scales with VIN, enabling stable operation across 6–42 V input while maintaining constant switching frequency in continuous conduction mode (CCM).

It uses internal 7-V linear regulator (VCC) for gate drive bias, bootstrap-driven high-side MOSFET with 20-ns rise/fall times, and dual protection comparators: CS pin monitors 200-mV regulation threshold and 300-mV overvoltage/overcurrent limit. Thermal shutdown activates at 165°C with 25°C hysteresis.

Key Specifications

Pinout & Package

LM3404MR/NOPB is housed in an 8-pin SO PowerPAD™ package (3.90 mm × 4.89 mm) with exposed thermal pad (DAP) that must be soldered to PCB ground plane using 4–6 thermal vias for optimal thermal performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar constant-current buck LED driver applications.

Compared with LM3404HVMM/NOPB, LM3404MR/NOPB trades input voltage headroom for cost and thermal efficiency in 12/24 V systems; versus MPQ4425AGU-AEC1-P, it provides greater design flexibility via RON programming and superior fault coverage at the expense of footprint size and automotive qualification.

Availability

LM3404MR/NOPB is available at Aetrix Electronics and suitable for automotive headlamps, industrial high-bay lighting, and commercial streetlight modules requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LM3404MR/NOPB 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 and embedded processing solutions across industrial, automotive, and personal electronics markets.

The LM3404MR/NOPB belongs to TI's LED driver product line, engineered specifically for high-reliability, thermally demanding constant-current applications in automotive exterior lighting and industrial solid-state illumination systems.

FAQ

What is the maximum LED string voltage supported by LM3404MR/NOPB?

The maximum output voltage of LM3404MR/NOPB is determined by its minimum off-time (300 ns) and programmed on-time. At VIN = 42 V and typical RON, VO(MAX) reaches ~38 V. This supports up to six 3 V white LEDs (18 V VF) plus margin for sensing and diode drop. For higher strings, use LM3404HVMM/NOPB (75 V input) or add external OVP clamping per Figure 18 in the datasheet. LM3404MR/NOPB itself does not regulate beyond VO(MAX) but withstands it safely in open-circuit conditions.

Can LM3404MR/NOPB operate without an output capacitor?

Yes, LM3404MR/NOPB is explicitly designed to support capacitor-less output configurations. Its COT control and current-mode operation stabilize the LED current without output capacitance, reducing solution size and eliminating electrolytic aging. A small 10-nF ceramic capacitor across the LED array is recommended to dampen inductor ringing. LM3404MR/NOPB maintains regulation and protection functions-including open-LED detection-even with no output capacitor installed.

How is LED current accuracy affected by temperature in LM3404MR/NOPB?

LM3404MR/NOPB maintains LED current accuracy primarily through its 200-mV CS reference voltage, which exhibits ±3 mV variation (±1.5%) over –40°C to +125°C. The current-sense resistor RSNS dominates overall accuracy; using a 0.5% tolerance, 50 ppm/°C part achieves ±2% total current error across temperature. The LM3404MR/NOPB datasheet confirms VREF-REG drift is less than ±0.01%/°C, making RSNS selection and layout the dominant accuracy factor-not the IC itself.

What thermal design guidance applies to LM3404MR/NOPB in SO PowerPAD-8 package?

For LM3404MR/NOPB in SO PowerPAD-8, TI specifies R_θJA = 44.7 °C/W with JEDEC-standard 2-layer board. To achieve 1.2 A continuous output at +85°C ambient, the PCB must provide ≥2.5 cm² of 2-oz copper connected to the DAP via ≥4 thermal vias (0.3 mm diameter). Avoid solder mask over the DAP; use solder paste stencil opening matching pad size. Thermal simulation should target T_J ≤125°C-LM3404MR/NOPB triggers shutdown at 165°C, but derating ensures reliability.

Does LM3404MR/NOPB support analog dimming in addition to PWM?

No, LM3404MR/NOPB supports only digital PWM dimming via the DIM pin. It does not include an analog dimming interface (e.g., variable current-sense reference or DAC-controlled bias). Attempting analog control on DIM violates its specified 0.8 V / 2.2 V logic thresholds and may cause erratic switching or latch-up. For analog dimming, consider TI's TLC59xx LED drivers or discrete op-amp-based current control with LM3404MR/NOPB as the power stage-but LM3404MR/NOPB itself only accepts clean PWM signals.