Monolithic Power Systems Inc. MP4689DN-LF-Z

Overview

MP4689DN-LF-Z 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 from 4.5V to 95V input, delivers up to 95% efficiency, and targets automotive headlight modules, industrial high-bay lighting, and outdoor signage requiring robust, capacitor-free LED current regulation.

For engineers reviewing the MP4689DN-LF-Z datasheet, MP4689DN-LF-Z pinout, MP4689DN-LF-Z application, or MP4689DN-LF-Z 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 with defined hysteresis thresholds.

Technical Context

The MP4689 employs adaptive hysteretic current-mode control: FB pin thresholds switch between 215 mV (turn-off) and 185 mV (turn-on) to maintain 200 mV average sensing voltage across R_FB, enabling ±3% LED current accuracy without compensation components. Its internal bootstrap regulator charges the BST-SW capacitor to ~5 V, powering the floating gate driver for the integrated high-side MOSFET.

Protection architecture includes cycle-by-cycle current limiting (2.9 A typical), thermal shutdown at 150°C with 20°C hysteresis, and LED short detection via FB pin monitoring (<10 µs fault response). UVLO activates below 3.65 V (falling) and releases above 4.0 V (rising), ensuring stable startup across wide input ranges.

Key Specifications

Pinout & Package

MP4689DN-LF-Z is housed in an SOIC-8 with exposed pad (SOIC-8 EP), optimized for thermal conduction via PCB copper area under the pad and multiple thermal vias. The exposed pad must be soldered directly to the GND plane for reliable operation at full load.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MPQ4689-AEC1, the MP4689DN-LF-Z omits automotive qualification overhead while retaining identical electrical behavior and thermal performance; versus LM3409HV, it integrates the high-side switch and bootstrap circuit, cutting BOM count by ≥3 components and improving board-level reliability.

Availability

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

Supply support for MP4689DN-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 over 20 years of leadership 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 transients, thermal stress, and long service life are critical design constraints.

FAQ

What is the maximum LED string voltage supported by MP4689DN-LF-Z?

The MP4689DN-LF-Z does not regulate output voltage directly-it regulates LED current via inductor-based buck topology. Maximum LED string voltage is limited by input voltage minus diode forward drop and switch saturation. With 95 V max VIN and typical Schottky V_F ≈ 0.4 V, practical string voltage reaches up to ~90 V (e.g., 25× 3.6 V white LEDs), confirmed in MPS application note AN-4689.

Can MP4689DN-LF-Z operate without an output capacitor?

Yes-MP4689DN-LF-Z is explicitly designed for capacitorless operation. Its hysteretic control and 15% LED current ripple meet IEC TR 61000-3-3 flicker limits for most commercial lighting. An output capacitor may be added only to further reduce ripple, but is not required for stability or basic functionality.

How is thermal performance affected if the exposed pad is not soldered to GND?

Without soldering the exposed pad to a thermal GND plane, θ_JA degrades from 50°C/W to >100°C/W, reducing safe continuous power dissipation by >50%. At 1 A output, junction temperature can exceed 150°C within seconds, triggering thermal shutdown. MPS datasheet Figure 9 confirms >20°C junction rise difference with and without pad connection.

What happens during LED open-circuit fault?

MP4689DN-LF-Z has no dedicated open-circuit protection. If the LED string opens, FB pin voltage drops to 0 V, causing the controller to continuously attempt switching. This results in high voltage at SW node (approaching VIN), potentially damaging the internal MOSFET or external diode. External overvoltage clamping or open-detection circuitry is recommended for safety-critical applications.

Is the DIM pin compatible with 3.3 V microcontroller GPIOs?

Yes-the DIM pin threshold is 0.8–1.5 V (rising), with ±1 µA input current. A 3.3 V GPIO driving DIM through a 10 kΩ pull-up meets all timing and voltage requirements. No level-shifting is needed, and propagation delay remains 50 ns, preserving 20 kHz dimming fidelity.

Does MP4689DN-LF-Z support analog dimming via FB pin voltage adjustment?

No-FB pin is a dedicated current-sense input with fixed 200 mV reference. Analog dimming is not supported. Only PWM dimming via the DIM pin is implemented; attempts to modulate FB voltage cause regulation instability and potential overcurrent conditions.

What is the minimum inductor value recommended for stable operation at 1 MHz?

MPS recommends ≥4.7 µH for 1 MHz operation with 1 A output. Lower values risk peak current exceeding 2.9 A limit and increased ripple. Application note AN-4689 specifies 47 µH for 200 kHz baseline, but 10 µH is validated at 1 MHz with 1 A load and 60 V input in MP4689 evaluation report EV4689-Q-00A.