Monolithic Power Systems Inc. MP4689DN-LF

Overview

MP4689DN-LF from Monolithic Power Systems is a 100V-input, 1A constant-current step-down LED driver IC with integrated high-side 100V MOSFET (R_DS(ON) = 500 mΩ), hysteretic current-mode control, ±3% LED current accuracy, and 20 kHz PWM dimming support. It operates across 4.5–95 V input, delivers up to 95% efficiency, and targets automotive headlight modules, industrial high-bay lighting, and outdoor signage requiring robust, capacitorless LED current regulation.

For engineers reviewing the MP4689DN-LF datasheet, MP4689DN-LF pinout, MP4689DN-LF application, or MP4689DN-LF equivalent, key selection criteria include its 200 mV feedback reference voltage, 170 µA quiescent current for battery-backed systems, SOIC-8 EP thermal performance (θ_JA = 50°C/W), and dedicated DIM/EN logic-level control inputs compatible with microcontroller GPIOs.

Technical Context

The MP4689DN-LF implements adaptive hysteretic current-mode control: FB pin thresholds switch between 185 mV (low) and 215 mV (high) to maintain 200 mV average sensing voltage across R_FB, enabling ±3% LED current accuracy without compensation components. Its internal 100V high-side MOSFET eliminates external switch requirements and supports up to 2.9 A peak current limiting.

Thermal shutdown activates at 150°C with 20°C hysteresis, and UVLO engages below 3.65 V (falling) / above 4.0 V (rising). The bootstrap regulator charges BST–SW to ~5 V, enabling gate drive for the floating high-side switch, while dedicated DIM and EN pins provide independent 0.8–1.5 V logic-controlled dimming and enable functionality.

Key Specifications

Pinout & Package

MP4689DN-LF is housed in an SOIC-8 with exposed pad (SOIC-8 EP), optimized for thermal conduction via PCB copper area and thermal vias under the pad. Pin 8 serves as both GND and thermal slug connection point.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MPQ4689DN-AEC1-LF, the MP4689DN-LF lacks automotive qualification but matches all electrical performance; versus LM3409HVMM/NOPB, it integrates the high-side switch and eliminates compensation, reducing component count and improving current accuracy at the cost of fixed 200 mV reference.

Availability

MP4689DN-LF is available at Aetrix Electronics and suitable for automotive headlamp modules, industrial high-bay luminaires, and outdoor digital signage requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MP4689DN-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 core expertise in DC/DC conversion, LED drivers, and motor control solutions.

The MP4689 belongs to MPS's high-voltage LED driver product line, engineered specifically for ruggedized constant-current regulation in automotive, industrial, and outdoor lighting where input voltage range, thermal reliability, and minimal external components are critical.

FAQ

What is the maximum LED string voltage the MP4689DN-LF can drive?

The MP4689DN-LF does not regulate output voltage directly; it regulates LED current. Maximum string voltage equals VIN minus minimum dropout - typically up to 95 V input minus ~2 V overhead, so ~93 V maximum LED forward voltage at full load. Layout and diode selection must sustain this voltage.

Can the MP4689DN-LF operate without an output capacitor?

Yes - the MP4689DN-LF is explicitly designed for capacitorless operation. Its hysteretic control maintains LED current with only 15% peak-to-peak ripple using only the series sense resistor and inductor; C_OUT is optional for further ripple reduction.

How is thermal performance affected by the exposed pad connection?

The exposed pad (Pin 8) is electrically GND and thermally critical: connecting it to ≥1 cm² of inner/outer PCB copper with ≥6 thermal vias (15 mil diameter, 40 mil pitch) reduces θ_JA from 50°C/W to ~35°C/W, enabling full 1 A operation at +70°C ambient.

What happens during LED short-circuit conditions?

Under LED short (e.g., R_FB failure or direct GND short), FB voltage collapses. The IC detects sustained low FB (<179 mV) for >10 µs, shuts off the high-side switch, waits ~300 µs, then retries. Simultaneously, peak current limit (2.9 A) provides secondary protection against MOSFET overcurrent.

Is the DIM pin compatible with standard microcontroller PWM outputs?

Yes - the DIM pin accepts logic-level PWM signals with 0.8 V (min) high threshold and 1.5 V (max) low threshold. Standard 3.3 V or 5 V MCU GPIOs drive it directly; propagation delay is 50 ns, supporting clean 20 kHz dimming without phase shift or jitter.

Does the MP4689DN-LF require a bootstrap diode?

No - the internal bootstrap regulator charges the BST capacitor from VIN. An external diode (e.g., BAT54) is optional and recommended only for high-duty-cycle (>65%) or >1.5 MHz operation to improve efficiency and stability; not required for standard 12–48 V applications.

What is the minimum inductor value for stable 1 A operation at 60 V input?

For 60 V input driving a 30 V LED string at 1 MHz, the recommended inductor is 47 µH. Lower values risk excessive peak current (>2.9 A) and instability; the datasheet specifies L ≥ 47 µH for full 1 A output with <15% ripple and margin against saturation at peak current.