Monolithic Power Systems Inc. MP3305DD-LF-P

Overview

MP3305DD-LF-P from Monolithic Power Systems is a 36V, 1.3A step-up white LED driver with fixed 2.2MHz switching frequency, true PWM dimming up to 50kHz, and adjustable open-load OVP threshold. It regulates LED current via external sense resistor with 200mV feedback voltage, supports up to 10-series WLED strings, and integrates internal 1.3A MOSFET switch for compact backlight solutions in small LCD displays.

For engineers reviewing the MP3305DD-LF-P datasheet, MP3305DD-LF-P pinout, MP3305DD-LF-P application, or MP3305DD-LF-P equivalent, key selection criteria include its 2.2MHz high-frequency operation enabling smaller magnetics, 200mV ISET reference minimizing sense loss, 50kHz true PWM dimming eliminating audible noise, and OVP threshold adjustment via external resistor divider for flexible open-circuit protection.

Technical Context

The MP3305DD-LF-P employs constant-frequency peak-current-mode boost architecture with integrated 0.4Ω power MOSFET (SW) and 0.8Ω LED-switch (M2), enabling efficient regulation of LED string current across input voltages from 2.5V to 6V. Its 2.2MHz oscillator and stabilizing ramp suppress subharmonic oscillation above 50% duty cycle.

Feedback control uses a precision 200mV reference at ISET pin to regulate current through an external resistor; OVP shutdown triggers at 0.9V on OVP pin, set by external divider; EN pin serves dual role as enable input and PWM dimming command interface (250Hz–50kHz square wave).

Key Specifications

Pinout & Package

MP3305DD-LF-P is housed in an 8-pin QFN package (2mm × 3mm, 0.5mm pitch) with exposed thermal pad connected to GND. The package enables high power density and low thermal resistance (θ_JA = 65°C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar step-up white LED driver applications.

Compared with RT9397BZSP and LM3409MYX/NOPB, MP3305DD-LF-P uniquely combines adjustable OVP, 50kHz true PWM dimming, and integrated 1.3A switch in a 2×3mm QFN-making it optimal for compact, noise-sensitive, and field-replaceable LED string applications.

Availability

MP3305DD-LF-P is available at Aetrix Electronics and suitable for LCD panels, digital picture frames, and handheld computers requiring stable component supply, RoHS-compliant packaging, and guaranteed long-term availability.

Supply support for MP3305DD-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, with design centers in the US, China, and Taiwan.

The MP3305 belongs to MPS's white LED driver product line, engineered specifically for high-efficiency, high-frequency backlighting in portable and space-constrained displays with stringent EMI and thermal requirements.

FAQ

What is the maximum number of white LEDs the MP3305DD-LF-P can drive?

The MP3305DD-LF-P supports up to 10-series white LEDs, assuming typical forward voltage of ~3.3V per LED and 36V maximum output. At higher forward voltages (e.g., cold temperature), the practical limit may reduce to 9 LEDs. Total string current is set by the ISET resistor and remains constant regardless of string count.

How is the OVP threshold adjusted on the MP3305DD-LF-P?

OVP threshold is set using a resistor divider from the LED string output to the OVP pin, where the voltage at OVP must reach 0.9V to trigger shutdown. For example, a 100kΩ top resistor and 10kΩ bottom resistor yields 0.9V at OVP when output reaches 9.9V. The formula is V_OVP = 0.9V × (1 + R_top/R_bottom).

Does the MP3305DD-LF-P support analog dimming in addition to PWM?

No-the MP3305DD-LF-P supports only true PWM dimming via the EN pin (250Hz–50kHz square wave). It does not provide analog dimming capability; LED current is regulated solely by the 200mV ISET reference and external resistor, with no provision for DC bias or voltage-controlled current scaling.

What is the recommended inductor value and type for MP3305DD-LF-P?

MPS recommends a 2.2µH shielded power inductor with ≤150mΩ DCR for 5V input and 200mA LED current. For higher input voltages (e.g., 6V), a 1.0–1.5µH inductor improves efficiency. Ferrite-core shielded types (e.g., TDK SPM series) minimize EMI and saturation risk at 2.2MHz switching.

Can the MP3305DD-LF-P operate from a 3.3V input source?

Yes-the MP3305DD-LF-P operates from 2.5V to 6V input, making it compatible with 3.3V rails. However, at 3.3V input driving 10-series LEDs (~33V total), duty cycle exceeds 90%, reducing efficiency and increasing thermal stress. Use minimum 4.5V input for full 10-LED capability.

Is the exposed thermal pad on the QFN package electrically connected?

Yes-the exposed pad is internally connected to GND and must be soldered to a PCB ground plane. It serves both electrical (low-impedance GND return) and thermal (65°C/W θ_JA) functions. Failure to connect it degrades efficiency, increases junction temperature, and risks thermal shutdown.

What protection features are integrated into the MP3305DD-LF-P?

The MP3305DD-LF-P integrates under-voltage lockout (2.45V rising), over-voltage protection (adjustable via OVP pin), over-current limiting (1.33A typical), and thermal shutdown (150°C). All protections are auto-recovering except OVP, which requires power cycle after shutdown.