Texas Instruments LM3404MAX

Overview

LM3404MAX from Texas Instruments is a monolithic 1-A constant-current buck regulator IC designed specifically 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. It is used in headlamp modules and streetlight drivers where stable current regulation and thermal robustness are critical.

For engineers reviewing the LM3404MAX datasheet, LM3404MAX pinout, LM3404MAX application, or LM3404MAX equivalent, key selection considerations include its 200-mV CS reference accuracy, programmable on-time control via R_ON, SOIC-8 PowerPAD™ package thermal performance (R_θJA = 44.7 °C/W), integrated 7-V VCC bias regulator, and open-LED protection capability using the CS overvoltage comparator.

Technical Context

The LM3404MAX employs a controlled-on-time (COT) hysteretic architecture that eliminates need for external loop compensation. Its on-time is set by an external resistor (RON) and inversely scales with VIN - e.g., 2.75 µs at 10 V and 675 ns at 40 V - enabling stable switching frequency in continuous conduction mode (CCM).

Current regulation is achieved by comparing the voltage across an external sense resistor (RSNS) to a precise 200-mV internal reference (VREF-REG = 200 mV ±3 mV). The CS pin also hosts a 300-mV overvoltage comparator for open-LED fault detection, while thermal shutdown activates at 165°C with 25°C hysteresis.

Key Specifications

Pinout & Package

LM3404MAX is housed in an SOIC-8 package with exposed PowerPAD™ (DDA variant), measuring 3.90 mm × 4.89 mm. The PowerPAD must be soldered to a 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, LM3404MAX offers identical performance in legacy-qualified packaging, while MPQ4425AGU-AEC1-P trades simplicity and fault protection for automotive qualification - making LM3404MAX optimal for cost-sensitive industrial and commercial LED systems where robustness and ease of use are prioritized.

Availability

LM3404MAX is available at Aetrix Electronics and suitable for automotive headlamps, industrial high-bay lighting, and streetlight LED drivers requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for LM3404MAX 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 specializing in analog and embedded processing technologies, with leadership in power management ICs and LED driver solutions.

The LM3404 family was engineered as a highly integrated, thermally robust constant-current buck controller for high-power LED lighting - targeting applications where reliability, small solution size, and simplified design outweigh the need for multi-topology flexibility.

FAQ

What is the maximum input voltage supported by the LM3404MAX?

The LM3404MAX supports a maximum input voltage of 42 V, with absolute maximum rating of 45 V. This makes it compatible with 24 V industrial systems and 12 V automotive platforms with transient surges. Operation above 42 V risks exceeding recommended conditions and may trigger thermal shutdown or reduce long-term reliability. Always refer to the Absolute Maximum Ratings table in the official LM3404MAX datasheet for safe design margins.

How does the LM3404MAX achieve constant LED current without external compensation?

The LM3404MAX uses a controlled-on-time (COT) hysteretic control architecture that compares the CS pin voltage against a 200-mV internal reference. When current falls below the setpoint, the internal MOSFET turns on for a VIN- and RON-determined on-time; no error amplifier or external compensation components are needed. This architecture inherently stabilizes in continuous conduction mode and eliminates phase-margin concerns - a key advantage of the LM3404MAX over traditional voltage-mode or current-mode controllers.

Can the LM3404MAX operate without an output capacitor?

Yes, the LM3404MAX supports capacitor-less operation due to its current-regulated buck topology and inherent stability. The inductor directly controls LED current ripple, eliminating need for output capacitance to maintain regulation. However, a small 10-nF capacitor across the LED string is recommended to dampen high-frequency ringing at the SW node. This capability reduces BOM cost and improves reliability in high-temperature or high-vibration environments where electrolytic capacitors degrade.

What is the function of the RON pin on the LM3404MAX?

The RON pin on the LM3404MAX sets the controlled on-time (t_ON) by connecting an external resistor between RON and VIN. t_ON scales inversely with VIN - e.g., ~2.75 µs at 10 V and ~675 ns at 40 V - which determines switching frequency and regulates output voltage headroom. Selecting RON adjusts trade-offs between efficiency, EMI, and minimum controllable output voltage. Incorrect RON values may cause unstable operation or inability to regulate low-VF LED strings.

Does the LM3404MAX provide protection against open-LED conditions?

Yes, the LM3404MAX includes built-in open-LED protection via the CS pin's 300-mV overvoltage comparator. During an open-circuit fault, VSNS drops to 0 V, causing the controller to command maximum duty cycle - but once VO rises enough to develop 300 mV across RSNS (i.e., I_F × R_SNS = 300 mV), the comparator disables the switch. This limits peak output voltage to VO(MAX) and prevents damage to the LED string or external components - a core safety feature of the LM3404MAX design.