Texas Instruments LM3404MRX/NOPB

Overview

LM3404MRX/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. 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. It is used in headlamp and fog lamp drivers where stable current regulation and thermal robustness are critical.

For engineers reviewing the LM3404MRX/NOPB datasheet, LM3404MRX/NOPB pinout, LM3404MRX/NOPB application, or LM3404MRX/NOPB equivalent, key selection considerations include its 200-mV current-sense threshold, programmable on-time via R_ON, SO PowerPAD-8 thermal performance (R_θJA = 44.7°C/W), integrated 7-V bias regulator, and open-LED protection capability.

Technical Context

The LM3404MRX/NOPB uses a controlled-on-time (COT) hysteretic architecture with an external R_ON-settable on-time and fixed 300-ns minimum off-time. It regulates LED current by comparing the voltage across an external sense resistor (RSNS) to a precise 200-mV reference at the CS pin, enabling valley-current control without loop compensation.

Its internal 7-V linear regulator powers gate drive and control circuitry from VIN, with undervoltage lockout at 5.3 V and bypass activation at 8.8 V. The high-side MOSFET driver employs a bootstrap circuit (CB = 10 nF ceramic) referenced to SW, supporting fast 20-ns rise/fall times and enabling operation up to 42 V input while maintaining efficient switching.

Key Specifications

Pinout & Package

LM3404MRX/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 (R_θJB = 24.5°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM3404MHX/NOPB, LM3404MRX/NOPB delivers superior thermal management for sustained 1-A loads in compact enclosures; versus TPS92630QPWPRQ1, it offers lower system cost and simpler analog implementation but lacks safety diagnostics and digital configurability.

Availability

LM3404MRX/NOPB is available at Aetrix Electronics and suitable for automotive headlamps, industrial high-bay lighting, and commercial street lighting requiring stable component supply, long-term production continuity, and RoHS-compliant packaging.

Supply support for LM3404MRX/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, specializing in analog, embedded processing, and digital signal processing technologies for industrial, automotive, and consumer markets.

The LM3404MRX/NOPB belongs to TI's LED lighting controller product line, engineered specifically for high-reliability, thermally demanding constant-current applications in automotive exterior lighting and industrial solid-state illumination.

FAQ

What is the maximum continuous output current of the LM3404MRX/NOPB?

The LM3404MRX/NOPB is rated for 1.2-A continuous output current over its full operating temperature range (–40°C to +125°C). This is achieved with proper thermal design using the SO PowerPAD package and adequate PCB copper area. Peak current limit is 1.5 A typical, triggering hiccup-mode protection if exceeded.

Does the LM3404MRX/NOPB require external compensation components?

No, the LM3404MRX/NOPB uses a controlled-on-time (COT) hysteretic control architecture that eliminates the need for external compensation networks. Its stability is inherent to the topology, allowing direct implementation with only passive components: inductor, Schottky diode, sense resistor, bootstrap capacitor, and input/output capacitors.

How does the DIM pin function on the LM3404MRX/NOPB?

The DIM pin on the LM3404MRX/NOPB accepts TTL-level PWM signals (V_IL ≤ 0.8 V, V_IH ≥ 2.2 V) to enable or disable the internal MOSFET, providing fast LED dimming without interrupting the internal bias circuitry. A 75-µA internal pullup ensures default-on operation when the pin is left floating, eliminating the need for an external pullup resistor.

Can the LM3404MRX/NOPB operate without an output capacitor?

Yes, the LM3404MRX/NOPB supports capacitor-less output configurations because it regulates LED current-not voltage-and the inductor directly feeds the LED string. This reduces bill-of-materials cost and board area. A small 10-nF capacitor across the LED array is recommended to dampen switching-node oscillations in such configurations.

What thermal performance can be expected from the LM3404MRX/NOPB in a standard 4-layer PCB layout?

In a standard 4-layer PCB with 2 oz copper, 4 thermal vias under the DAP, and 1 in² of 2 oz inner-layer ground copper, the LM3404MRX/NOPB achieves R_θJA ≈ 44.7°C/W. At 1.2-A load and 24-V input, junction temperature rise is approximately 54°C above ambient-well within the 125°C max rating at 70°C ambient.