Monolithic Power Systems Inc. MP3391EY-LF-P

Overview

MP3391EY-LF-P from Monolithic Power Systems is an 8-channel, 120mA/channel step-up WLED driver controller designed for large LCD panel backlighting. It uses fixed-frequency current-mode control, drives an external N-MOSFET, regulates LED string current via ISET resistor (±2.5% matching), supports programmable switching frequency (60–900 kHz), and delivers 9V–35V input operation with internal 10V VDD and 5V VCC regulators.

For engineers reviewing the MP3391EY-LF-P datasheet, MP3391EY-LF-P pinout, MP3391EY-LF-P application, or MP3391EY-LF-P equivalent, key selection criteria include LED string count configuration (4/6/8), open/short protection thresholds (SSET/TSET), PWM/DC dimming mode flexibility, OVP programming via resistor divider, and thermal shutdown at 150°C.

Technical Context

The MP3391EY-LF-P implements a peak-current-mode step-up converter with programmable oscillator (ROSC) and dual internal linear regulators (VDD=10V, VCC=5V). Its 8-channel current sources use open-drain LEDx outputs with 450mV regulation voltage and 2.5% inter-string matching accuracy.

Protection architecture includes programmable short-LED detection (via SSET voltage threshold ×4.5), timer-based fault latching (TSET capacitor), over-voltage protection (OVP pin threshold = 1.24V), and fault flag output (FF pin pulled low on open/short event).

Key Specifications

Pinout & Package

MP3391EY-LF-P is housed in a 28-pin SOIC package with exposed pad (SOIC28), rated for -20°C to +85°C ambient operation and 2.1W continuous power dissipation at TA=25°C.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar WLED backlight controller applications.

Compared with MP3391EY-LF-P, MPQ3367-AEC1 offers automotive reliability but sacrifices configurability and external FET drive, while LM3409QMY/NOPB reduces channel count and shifts complexity to external components - making MP3391EY-LF-P optimal for cost-sensitive, flexible, large-panel backlight systems.

Availability

MP3391EY-LF-P is available at Aetrix Electronics and suitable for desktop LCD flat panel displays, LCD TVs and monitors, and industrial human-machine interfaces requiring stable component supply, RoHS compliance, and long-term production continuity.

Supply support for MP3391EY-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, and global manufacturing partnerships.

The MP3391 product line targets large-format LCD backlighting applications, emphasizing high channel count, precision current matching, integrated protection, and flexible dimming to replace discrete LED driver solutions in display electronics.

FAQ

What is the maximum number of LED strings supported by MP3391EY-LF-P?

The MP3391EY-LF-P supports up to 8 LED strings simultaneously. The actual count is configured via the NUMSEL pin: floating enables all 8 strings (LED1–LED8), high logic level enables 6 strings (LED1–LED6), and low logic level enables 4 strings (LED1–LED4). This pin is not internally pulled, so external biasing is required for defined 4- or 6-string operation.

How is LED current accuracy achieved across channels?

MP3391EY-LF-P achieves ±2.5% current matching between strings using matched internal current sources and a shared 1.23V ISET reference. Each LEDx pin operates as an open-drain current sink regulated to maintain identical voltage drop across external sense resistors, minimizing process- and temperature-induced mismatches without requiring per-channel calibration.

Can MP3391EY-LF-P operate without an external MOSFET?

No. MP3391EY-LF-P is a controller-only device and requires an external N-channel power MOSFET connected to the GATE pin. It provides 10V gate drive (VDD) capable of sourcing 400mA and sinking 1A, but contains no integrated power switch. Operation without an external MOSFET will result in no boost conversion or LED current regulation.

What protection features does MP3391EY-LF-P provide for LED string faults?

It provides open-string detection (via OVP and LEDx voltage monitoring), short-string protection (programmed via SSET and timed by TSET capacitor), over-voltage protection (OVP pin threshold = 1.24V), thermal shutdown (150°C), and fault flag reporting (FF pin pulled low). All protections latch until device reset via EN toggle or power cycle.

Is MP3391EY-LF-P compatible with both PWM and analog dimming inputs?

Yes. The DBRT pin accepts either a 100Hz–20kHz external PWM signal for direct dimming control, or a 0.2–1.2V DC voltage for linear brightness adjustment. When using DC input, the BOSC pin capacitor sets the internal dimming frequency (1.2–1.6 kHz typical), converting the analog level into a proportional-duty-cycle DPWM waveform.

What is the purpose of the VFAULT pin?

VFAULT is a PMOS gate driver output used to disconnect the input supply from the boost circuit during fault conditions. When enabled, it turns on an external high-side PMOS to connect VIN to the boost stage; during shutdown or short-circuit events, it turns off the PMOS to isolate input from output, enhancing system safety and enabling hot-swap capability.

Does MP3391EY-LF-P require external compensation components?

Yes. The COMP pin requires an external RC network (typically 1–10kΩ series resistor + 1–10nF capacitor to GND) to stabilize the step-up converter's feedback loop. Compensation values depend on selected inductor, output capacitance, and load conditions; MPS Application Note AN-107 provides design guidelines and stability analysis methods.