Monolithic Power Systems Inc. MP4688DN-LF-Z

Overview

MP4688DN-LF-Z from Monolithic Power Systems is a high-voltage, constant-current LED driver IC with integrated 80V high-side MOSFET, delivering up to 1A LED current with ±5% accuracy, 2MHz switching frequency, and 20kHz PWM dimming capability. It operates from 4.5V–75V input and targets automotive headlight modules, industrial high-bay lighting, and streetlamp drivers requiring robust overvoltage and thermal protection.

For engineers reviewing the MP4688DN-LF-Z datasheet, MP4688DN-LF-Z pinout, MP4688DN-LF-Z application, or MP4688DN-LF-Z equivalent, key selection criteria include its hysteresis current-mode control (no compensation required), 170µA quiescent current for battery-backed systems, 200mV feedback reference voltage, and SOIC8E exposed-pad thermal performance (θJA = 50°C/W).

Technical Context

The MP4688DN-LF-Z implements adaptive hysteresis current-mode control: FB pin thresholds shift between 185mV (turn-off) and 215mV (turn-on) to maintain 200mV average feedback voltage, enabling ±5% LED current regulation without external compensation. Its internal 3.2A current limit and integrated high-side MOSFET (RDS(ON) = 360mΩ typ.) eliminate external switch requirements.

Thermal shutdown activates at 150°C with 20°C hysteresis; short-circuit protection responds within 10µs when FB voltage fails to rise, followed by 300µs retry cycle. The dedicated DIM pin accepts 0.8–1.5V logic thresholds for precise 20kHz PWM dimming, independent of EN control.

Key Specifications

Pinout & Package

The MP4688DN-LF-Z is packaged in SOIC8E (exposed pad), offering 2.5W continuous power dissipation at +25°C ambient and θJA = 50°C/W on a 4-layer board. Exposed pad must be soldered to PCB ground plane using thermal vias for optimal junction temperature management.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MPQ4688-AEC1, the MP4688DN-LF-Z offers identical performance at lower cost for non-automotive use, while LM3409HV demands external FET and compensation but provides greater flexibility in high-current or multi-string configurations.

Availability

MP4688DN-LF-Z is available at Aetrix Electronics and suitable for automotive headlight modules, industrial high-bay lighting, and streetlamp drivers requiring stable component supply across multi-year production cycles.

Supply support for MP4688DN-LF-Z 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 core expertise in DC-DC conversion, LED drivers, and motor control.

The MP4688 belongs to MPS's high-voltage LED driver product line, engineered specifically for ruggedized constant-current regulation in automotive and outdoor lighting where input transients, thermal stress, and long service life are critical design constraints.

FAQ

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

The MP4688DN-LF-Z does not regulate output voltage directly-it regulates LED current via inductor-based buck topology. Maximum LED string voltage equals VIN minus diode forward drop and switch saturation voltage. With 75V max VIN and typical 0.4V Schottky drop, up to 74V LED string voltage is feasible, limited only by external component ratings.

Can MP4688DN-LF-Z operate without an output capacitor?

Yes-MP4688DN-LF-Z is explicitly designed for capacitorless operation. Its hysteresis control maintains 15% peak-to-peak LED current ripple without COUT. An output capacitor may be added only to further reduce ripple, but it is not required for stability or basic functionality.

How does the DIM pin interact with the EN pin during startup?

DIM and EN are fully independent inputs. EN controls global device enable/disable (with 1.5V threshold), while DIM controls PWM dimming duty cycle. If DIM is held low during EN assertion, LEDs remain off until DIM rises above 0.8V. No timing interlock or priority logic exists between them.

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

For 2MHz switching at 730mA LED current and 60V VIN driving a 40V LED string, the datasheet recommends ≥47µH. Lower values increase peak inductor current and ripple, risking saturation. Use shielded power inductors rated for ≥1.5A DC and 3A peak to ensure reliable 2MHz operation.

Is the exposed pad on MP4688DN-LF-Z electrically connected to GND?

Yes-the exposed pad is internally bonded to the IC's GND potential and must be soldered to the PCB's main GND plane. Thermal vias (15mil diameter, 40mil pitch) are required beneath the pad to achieve the specified θJA = 50°C/W and prevent junction temperature exceedance at full load.

Does MP4688DN-LF-Z support analog dimming via the FB pin?

No-MP4688DN-LF-Z supports only PWM dimming via the dedicated DIM pin. Analog dimming by injecting current into FB is not supported; the FB pin is a high-impedance input for sensing only, with ±300nA input current specified. Attempting analog control risks regulation instability and accuracy loss.

What failure protections activate if the LED string opens?

Open-LED detection is not implemented. With no current path, FB voltage remains near 0V, causing the high-side MOSFET to stay continuously on. Protection relies on external circuitry (e.g., open-LED comparator monitoring SW node) or system-level supervision-MP4688DN-LF-Z only protects against short circuits and thermal overload.