Texas Instruments LM3404MRX

Overview

LM3404MRX from Texas Instruments is a monolithic 1-A constant-current buck regulator IC designed to drive 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, regulates LED current via 200-mV CS pin reference, supports PWM dimming on the DIM pin, and delivers stable output without control-loop compensation.

For engineers reviewing the LM3404MRX datasheet, LM3404MRX pinout, LM3404MRX application, or LM3404MRX equivalent, key selection considerations include its hysteretic controlled-on-time (COT) architecture, 1.5-A cycle-by-cycle current limit, thermal shutdown at 165°C, SO PowerPAD-8 package for enhanced thermal performance, and compatibility with ceramic-only or capacitor-less output configurations.

Technical Context

The LM3404MRX implements a controlled-on-time (COT) buck topology with hysteretic feedback - eliminating need for external compensation components. Its on-time is programmable via R_ON resistor and inversely scales with VIN, enabling stable switching frequency in continuous conduction mode (CCM) across wide input ranges.

It features integrated 7-V linear regulator (VCC pin), bootstrap gate drive (BOOT–SW), fast 20-ns MOSFET switching transitions, and dual protection comparators: 200-mV valley current sense (CS) for regulation and 300-mV overcurrent/overvoltage clamp for open-LED fault handling.

Key Specifications

Pinout & Package

LM3404MRX is housed in an 8-pin SO PowerPAD™ package with exposed thermal pad (DAP) requiring connection to PCB ground plane via 4–6 vias for optimal thermal performance.

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 offers superior thermal performance via PowerPAD, enabling full 1-A operation in compact enclosures; versus MPQ4425HGJ-P, it trades external compensation flexibility for plug-and-play stability and lower BOM count in cost-sensitive lighting designs.

Availability

LM3404MRX is available at Aetrix Electronics and suitable for automotive lighting, industrial high-bay fixtures, and commercial streetlight systems requiring stable component supply, long-term manufacturability, and qualified thermal performance.

Supply support for LM3404MRX 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 automotive, industrial, personal electronics, and communications markets.

The LM3404 product line was engineered specifically for high-reliability constant-current LED driving in harsh environments - emphasizing thermal robustness, fault protection, and minimal external component count for lighting OEMs.

FAQ

What is the maximum input voltage rating for LM3404MRX?

The LM3404MRX has an absolute maximum VIN rating of 45 V, with recommended operating range from 6 V to 42 V. This makes it suitable for 12 V and 24 V automotive and industrial systems where transient spikes up to 45 V may occur. Exceeding 45 V risks permanent damage per Absolute Maximum Ratings table in the SNVS465G datasheet. The LM3404MRX must not be substituted with the LM3404HV variant unless input exceeds 42 V, as their voltage ratings differ.

Does LM3404MRX require external compensation components?

No, the LM3404MRX uses a controlled-on-time (COT) hysteretic control architecture that eliminates the need for external compensation components such as type-II or type-III error amplifier networks. Stability is inherent due to the one-shot on-timer and comparator-based feedback. This simplifies design, reduces bill-of-materials cost, and improves immunity to layout parasitics - a key advantage confirmed in Section 7.1 and Feature List of the LM3404MRX datasheet.

How does the DIM pin function on LM3404MRX?

The DIM pin on LM3404MRX is a TTL-compatible PWM dimming input: logic low (≤0.8 V) disables the internal MOSFET and halts LED current, while logic high (≥2.2 V) enables regulation. It features a 75-µA internal pullup, ensuring default ON operation when left unconnected. The LM3404MRX supports dimming frequencies up to ~1 kHz, provided f_DIM is at least one decade below the switching frequency to avoid aliasing - as specified in Section 7.3.7 of the LM3404MRX datasheet.

Can LM3404MRX operate without an output capacitor?

Yes, the LM3404MRX supports capacitor-less output configurations due to its current-mode buck topology and direct inductor-to-LED connection. The device maintains regulation by controlling inductor current ripple (Δi_L) rather than output voltage. Section 8.1.3 of the LM3404MRX datasheet explicitly confirms this capability and notes that a small 10-nF capacitor across the LED array suppresses switching-node oscillation - making it viable for space-constrained or high-reliability lighting applications.

What thermal metrics define LM3404MRX's SO PowerPAD-8 package performance?

The LM3404MRX in SO PowerPAD-8 package has R_θJB = 24.5°C/W (junction-to-board) and R_θJA = 44.7°C/W (junction-to-ambient), per Table 6.4 of the datasheet. These values assume proper PCB thermal design: DAP soldered to solid ground plane with 4–6 thermal vias. This enables 1.2-A continuous operation at +85°C ambient without forced air - significantly outperforming the SOIC-8 variant (R_θJA = 106.8°C/W). The LM3404MRX's thermal performance is validated under JEDEC JESD51-7 test conditions.