Monolithic Power Systems Inc. MP4688DN-LF

Overview

MP4688DN-LF from Monolithic Power Systems is a high-voltage step-down LED driver IC integrating a 80V-rated high-side MOSFET with 3.2A current limit, delivering up to 1A constant LED current. It operates from 4.5V–75V input, uses hysteresis current-mode control for 20kHz PWM dimming, and achieves ±5% LED current accuracy via 200mV feedback reference. Used in automotive headlamp modules and industrial high-bay lighting.

For engineers reviewing the MP4688DN-LF datasheet, MP4688DN-LF pinout, MP4688DN-LF application, or MP4688DN-LF equivalent, key selection criteria include input voltage range (4.5–75V), integrated MOSFET R_DS(ON) (360mΩ), thermal shutdown threshold (150°C), dimming frequency support (up to 20kHz), and SOIC8E exposed-pad thermal performance (θ_JA = 50°C/W).

Technical Context

The MP4688DN-LF implements hysteresis current-mode control with adaptive 185mV/215mV FB thresholds to maintain 200mV average reference-enabling accurate LED current regulation without external compensation. Its dedicated DIM pin accepts logic-level PWM signals with 50ns propagation delay, supporting flicker-free dimming at up to 20kHz.

Internal bootstrap regulation charges the BST capacitor to ~5V for high-side gate drive; UVLO (4.0V rising / 3.65V falling) and thermal shutdown (150°C trip, 130°C hysteresis) ensure robust fault tolerance. The integrated 3.2A current limit and short-circuit protection respond within 10µs.

Key Specifications

Pinout & Package

MP4688DN-LF is supplied in an SOIC8E (exposed pad) package optimized for thermal dissipation (θ_JA = 50°C/W). The exposed pad must be soldered to a PCB ground plane using ≥6 thermal vias (15mil barrel, 40mil pitch) for reliable 1A continuous operation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage LED driver applications.

Compared with MPQ4688-AEC1, the MP4688DN-LF offers identical functionality at lower cost and qualification overhead for non-automotive use; versus LM3409HV, it reduces component count by 6+ parts but trades off design flexibility for integration.

Availability

MP4688DN-LF is available at Aetrix Electronics and suitable for automotive headlamp modules, industrial high-bay lighting, and streetlight LED drivers requiring stable component supply across extended product lifecycles.

Supply support for MP4688DN-LF 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

Monolithic Power Systems (MPS) is a fabless semiconductor company specializing in high-performance analog and power ICs, with design centers in the US, China, and Taiwan.

The MP4688 belongs to MPS's high-voltage LED driver product line, engineered specifically for robust, high-efficiency constant-current regulation in harsh-input environments like automotive and outdoor lighting.

FAQ

What is the maximum recommended LED string voltage for MP4688DN-LF?

The MP4688DN-LF supports output voltages up to VIN – 3V under typical conditions. With 75V max input and 3.2A current limit, the practical LED string voltage is ≤72V. For 3.5V-per-LED white LEDs, this allows up to 20 LEDs in series. Exceeding this risks violating the SW node voltage rating or triggering overcurrent protection.

Can MP4688DN-LF operate without an output capacitor?

Yes-the MP4688DN-LF is explicitly designed to operate without an output capacitor. Its hysteresis control maintains ≤15% LED current ripple using only the inductor and sense resistor. Adding C_OUT further reduces ripple but is optional and introduces additional ESR-related losses and potential stability concerns.

How does the DIM pin interface with microcontrollers?

The DIM pin accepts standard 3.3V or 5V logic-level PWM signals directly. Its 0.8–1.5V rising threshold and 50ns propagation delay allow clean switching at frequencies up to 20kHz. No external level-shifter or pull-up is needed; MCU GPIO can drive it with ≥1mA sink/source capability.

What thermal vias configuration is required for SOIC8E exposed pad reliability?

A minimum of six 15mil-diameter thermal vias (0.38mm), spaced on a 40mil (1.02mm) center-to-center grid, must connect the exposed pad to an internal or bottom-layer solid GND plane. Via barrels must be filled during plating to prevent solder wicking and ensure <1.5°C/W thermal resistance from junction to PCB.

Is the FB pin compatible with remote LED sensing?

No-the FB pin senses voltage across a single, local sense resistor placed between LED cathode and GND. Remote sensing is not supported; layout best practice requires routing the FB trace away from noisy SW and inductor nodes, ideally on a layer opposite the inductor with ground-plane shielding.

Does MP4688DN-LF support analog dimming via the DIM pin?

No-the DIM pin is strictly digital PWM-only. Analog dimming (voltage-controlled current reduction) is not supported. For analog control, an external DAC or potentiometer must modulate the FB reference via a summing circuit-but this voids the ±5% accuracy guarantee and requires re-characterization.

What is the minimum inductor value for stable 1A operation at 75V input?

Per MPS application guidance, a 47µH inductor is validated for 1A output at 75V input. Smaller values increase peak current and switching losses; larger values reduce ripple but lower frequency and require physically larger cores. Inductor saturation current must exceed 1.075 × I_LED + (V_IN × 10⁻⁸) / L ≈ 1.15A.