Monolithic Power Systems Inc. MP3391EF-LF-P

Overview

MP3391EF-LF-P from Monolithic Power Systems is an 8-channel, 120mA/channel step-up WLED driver controller with current-mode fixed-frequency architecture, programmable switching frequency (60–900 kHz), 2.5% inter-string current matching, and integrated 10V gate driver for external N-MOSFET-designed for large LCD panel backlighting requiring precise per-string current regulation across 4/6/8 LED strings.

For engineers reviewing the MP3391EF-LF-P datasheet, MP3391EF-LF-P pinout, MP3391EF-LF-P application, or MP3391EF-LF-P equivalent, key selection criteria include input voltage range (9–35 V), LED string count configurability via NUMSEL, dual PWM/DC dimming modes, open/short LED protection thresholds, and thermal shutdown at 150°C.

Technical Context

The MP3391EF-LF-P implements a peak-current-mode boost converter with programmable oscillator (via OSC pin resistor) and internal error amplifier regulating output bus voltage to meet the highest forward voltage among active LED strings. It uses eight matched open-drain current sinks (LED1–LED8) referenced to a stable 1.23 V ISET voltage, achieving ±2.5% current matching across strings.

Protection logic includes programmable short-LED detection (via SSET/TSET), overvoltage protection (OVP pin threshold at 1.24 V), open-string fault flagging (FF pin pulled low), and VFAULT-controlled PMOS disconnect. Dimming is implemented either by external PWM on DBRT or internally generated DPWM using BOSC capacitor timing.

Key Specifications

Pinout & Package

MP3391EF-LF-P is housed in a RoHS-compliant, lead-free 28-pin TSSOP package (JEDEC MO-153, 9.7 mm × 4.4 mm, 0.65 mm pitch) with exposed thermal pad (PGND-connected) for enhanced power dissipation (θ_JA = 32 °C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP3391EF-LF-P, MP3394EF-LF-Z offers greater channel scalability but reduced per-string current capability, while LM3409QMY/NOPB provides topology flexibility at the cost of increased BOM count, layout complexity, and absence of factory-trimmed current matching.

Availability

MP3391EF-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, long-lifecycle support, and RoHS-compliant packaging.

Supply support for MP3391EF-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 core expertise in DC/DC conversion, LED drivers, and motor control solutions.

The MP3391 belongs to MPS's WLED backlight controller product line, engineered specifically for large-format LCD backlighting with emphasis on current accuracy, fault resilience, and seamless integration into display power architectures.

FAQ

What is the minimum recommended input capacitance for MP3391EF-LF-P?

A minimum 4.7 µF X5R/X7R ceramic capacitor is required at VIN, paralleled with a 220 µF electrolytic capacitor to suppress high-frequency switching noise and limit surge current. This configuration ensures stable operation across the full 9–35 V input range and prevents voltage droop during transient load steps.

How does the MP3391EF-LF-P handle open LED string faults?

When an LED string opens, the corresponding LEDX pin voltage drops below 190 mV; the IC marks off that string, maintains regulation using remaining strings, and pulls FF low. If all strings open, the boost converter shuts down. The fault remains latched until EN is cycled or VCC is re-applied.

Can MP3391EF-LF-P drive LEDs with forward voltages exceeding 35 V?

No - the maximum output voltage is limited by the external MOSFET's V_DS(max) rating and the OVP threshold setting. With 35 V input and typical boost ratios, practical output is ≤60 V. For higher V_f strings, use a cascaded or flyback architecture instead.

What is the purpose of the VFAULT pin and how should it be used?

VFAULT is a driver output for an external high-side PMOS transistor. During normal operation, it turns on to connect input to output; during fault (open/short LED, OVP, thermal shutdown), it turns off to isolate the input supply - preventing fault propagation and enabling safe system-level recovery.

Is the MP3391EF-LF-P compatible with I²C or SPI interface for digital dimming control?

No - MP3391EF-LF-P supports only analog (DC voltage) or PWM-based dimming via DBRT and BOSC pins. It has no digital communication interface. For digitally addressable dimming, consider MPS's MPQ3367 or similar I²C-configurable WLED drivers.

How is the switching frequency calculated from the OSC resistor value?

Switching frequency is calculated as f_SW(kHz) = 17000 / (10 + R_OSC in kΩ). For example, a 50 kΩ resistor yields ~283 kHz. This relationship is validated across temperature and process corners per the Rev. 1.12 datasheet Figure 10.

Does the MP3391EF-LF-P require external compensation components on the COMP pin?

Yes - a series RC network (e.g., 10 kΩ + 1 nF) or single capacitor (e.g., 100 pF–1 nF) must be connected from COMP to GND to stabilize the current-mode control loop. The exact values depend on inductor, output capacitor, and operating point, and are detailed in the Application Information section of the datasheet.