Monolithic Power Systems Inc. MP4688DN-LF-P

Overview

MP4688DN-LF-P 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 with ±5% accuracy at 200mV FB reference. It operates from 4.5V–75V input, supports 20kHz PWM dimming, and achieves up to 95% efficiency in SOIC8E package with exposed thermal pad. Used in automotive headlamp modules requiring stable current regulation under wide-input transients.

For engineers reviewing the MP4688DN-LF-P datasheet, MP4688DN-LF-P pinout, MP4688DN-LF-P application, or MP4688DN-LF-P equivalent, key selection criteria include its hysteresis current-mode control architecture, 170µA quiescent current for battery-backed lighting, 2MHz max switching frequency enabling compact magnetics, and integrated short-circuit/thermal protection without external sensing components.

Technical Context

The MP4688 employs hysteresis current-mode control with adaptive 185mV/215mV FB thresholds to maintain 200mV average feedback voltage-enabling fast transient response and eliminating compensation networks. Its internal high-side MOSFET (R_DS(ON) = 360mΩ typ) and dedicated bootstrap regulator drive the SW node up to 80V, supporting buck topology with no output capacitor required.

Enable and DIM inputs operate with precise thresholds (VENH = 1.55V, VDIMH = 1.15V) and low leakage (<1µA), allowing direct microcontroller interfacing. Thermal shutdown activates at 150°C with 20°C hysteresis, and short-circuit protection responds within 10µs by disabling the switch and retrying after 300µs.

Key Specifications

Pinout & Package

MP4688DN-LF-P is supplied in SOIC8E (exposed pad) package per JEDEC MS-012 BA, with thermal resistance θ_JA = 50°C/W and θ_JC = 10°C/W - optimized for high-power dissipation in LED driver applications.

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-P offers identical performance at lower cost but lacks automotive qualification; versus LT3762, it delivers simpler integration and wider input range but caps at 1A output - making it optimal for cost-sensitive, non-automotive 4.5–75V LED systems.

Availability

MP4688DN-LF-P is available at Aetrix Electronics and suitable for automotive headlamps, industrial high-bay fixtures, streetlight modules, and emergency exit signs requiring stable component supply across multi-year production cycles.

Supply support for MP4688DN-LF-P 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, headquartered in Kirkland, WA, with global design and support centers.

The MP4688 belongs to MPS's high-voltage LED driver product line, engineered specifically for automotive and industrial lighting applications demanding wide-input operation, high efficiency, and integrated protection - not general-purpose DC-DC conversion.

FAQ

What is the maximum LED string voltage supported by MP4688DN-LF-P?

The MP4688DN-LF-P does not regulate output voltage directly; it regulates LED current. The maximum LED string voltage equals VIN minus the forward drop across the external Schottky diode and inductor DCR. With 75V VIN and typical 0.4V diode drop, up to 74.6V LED string voltage is feasible - sufficient for 20+ 3.2V white LEDs in series.

Can MP4688DN-LF-P operate without an external bootstrap capacitor?

No. The BST pin requires a 0.1µF ceramic capacitor connected between BST and SW pins to charge the internal high-side gate driver. Omitting this capacitor prevents proper MOSFET turn-on, causing immediate failure to start or erratic switching. An external 5V-fed bootstrap diode (e.g., BAT54) is optional for high-duty-cycle operation but not a replacement for the capacitor.

How is LED current accuracy affected by temperature?

The ±5% LED current accuracy is specified over –40°C to +125°C junction temperature. Internal circuitry compensates for FB reference drift and MOSFET R_DS(ON) variation, maintaining 200mV average FB voltage across temperature - verified by characterization data in Rev. 1.2 datasheet Figure 12 (ILED vs. TJ).

Is the N/C pin (Pin 2) required to be grounded or left floating?

Pin 2 is internally unconnected and must remain electrically isolated - neither grounded nor tied to any net. Routing a trace to it or placing a via may cause parasitic coupling or manufacturing defects. The datasheet explicitly states "Not connected" with no recommended termination.

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

No. The DIM pin is digital-only: voltages below 0.8V disable LED current, and voltages above 1.5V enable full current. Analog dimming requires varying the FB reference, which is fixed internally. For analog control, use a current-sense resistor with variable gain amplifier feeding FB - but this voids the ±5% accuracy guarantee.

What is the minimum inductor value recommended for stable operation at 2MHz?

At 2MHz switching frequency and 75V input driving a 36V LED string, the minimum recommended inductor is 4.7µH (based on Equation 1 in datasheet page 8). Using smaller values risks peak current exceeding 3.2A OCP threshold and induces excessive current ripple (>15%), degrading LED lifetime and color consistency.

How does thermal shutdown interact with the exposed pad soldering?

Thermal shutdown triggers at 150°C junction temperature. With inadequate thermal vias or incomplete solder paste coverage on the exposed pad, θ_JA rises from 50°C/W to >70°C/W - causing premature shutdown at ~115°C ambient. Full pad soldering with ≥6 thermal vias is mandatory to achieve rated 2.5W power dissipation.