Monolithic Power Systems Inc. MP3391EF-LF-Z

Overview

MP3391EF-LF-Z from Monolithic Power Systems is an 8-channel, 120mA/channel step-up WLED driver controller for large LCD panel backlighting. It uses fixed-frequency current-mode control, drives an external N-MOSFET, accepts 9–35V input, regulates LED string current via ISET resistor (±2.5% matching), and supports programmable switching frequency (60–900 kHz) and dual-mode PWM/DC dimming. Used in LCD TVs and flat-panel monitors requiring precise multi-string current balance.

For engineers reviewing the MP3391EF-LF-Z datasheet, MP3391EF-LF-Z pinout, MP3391EF-LF-Z application, or MP3391EF-LF-Z equivalent, this page delivers verified technical context on its boost converter architecture, 8-channel open-drain current sources, VDD/VCC dual regulators, fault flag signaling (FF), and short/open LED protection thresholds - all critical for backlight BOM validation and thermal-aware layout.

Technical Context

The MP3391EF-LF-Z implements a peak-current-mode step-up controller with programmable oscillator (via OSC pin resistor) and dual internal linear regulators: VDD (10V, gate driver supply) and VCC (5V, control logic supply). Its 8-channel current regulation relies on matched internal current sinks tied to LEDx pins, each with ≤450mV compliance voltage.

Protection logic includes OVP (triggered at 1.24V on OVP pin), short-LED detection (via SSET-programmed threshold ×4.5), and open-LED detection (LEDx UVLO at 190mV), all feeding into FF pin fault flag assertion. Dimming is implemented either by external PWM on DBRT or internally generated DPWM using BOSC capacitor timing.

Key Specifications

Pinout & Package

MP3391EF-LF-Z is housed in a RoHS-compliant 28-pin TSSOP package (JEDEC MO-153, 9.7mm × 4.4mm), optimized for thermal dissipation in backlight power stages. Pin 28 is NC; PGND (Pin 23) and GND (Pin 8) are separate analog/digital grounds requiring star-point connection.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP3391EF-LF-Z, MP3394EF-LF-Z offers greater channel density but reduced thermal headroom in TSSOP28, while LM3409QMY/NOPB provides topology flexibility at the cost of multi-string precision - making MP3391EF-LF-Z optimal for cost-sensitive, high-uniformity 8-string LCD backlight designs.

Availability

MP3391EF-LF-Z is available at Aetrix Electronics and suitable for LCD TV backlighting, professional monitor illumination, and commercial signage applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

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

The MP3391 belongs to MPS's WLED backlight controller product line, designed specifically for energy-efficient, high-reliability LCD panel illumination with integrated fault protection and flexible dimming.

FAQ

What is the maximum number of LED strings supported by MP3391EF-LF-Z?

The MP3391EF-LF-Z supports up to 8 LED strings simultaneously. The actual count (8, 6, or 4) is determined by the NUMSEL pin: floating enables all 8 channels (LED1–LED8), a logic high selects 6 strings (LED1–LED6), and a logic low configures 4 strings (LED1–LED4). This configuration is hardware-selectable without firmware changes.

How is LED current accuracy achieved across channels?

MP3391EF-LF-Z achieves ±2.5% current matching between strings using matched internal current sinks referenced to a stable 1.23V ISET voltage. Each LEDx pin operates as an open-drain current sink with ≤450mV compliance voltage, minimizing process- and temperature-induced mismatch. No external calibration or trimming is required.

Can MP3391EF-LF-Z operate without an external MOSFET?

No. MP3391EF-LF-Z is a controller-only IC and requires an external N-channel power MOSFET connected to the GATE pin. It does not integrate a power switch. The GATE driver provides 10V (VDD) output with 0.4A source / 1A sink capability to ensure fast, low-loss switching of discrete MOSFETs rated for ≥40V V_DS.

What protection features does MP3391EF-LF-Z include?

It integrates open-LED detection (via OVP and LEDx UVLO at 190mV), short-LED protection (programmable threshold via SSET ×4.5 and timer via TSET capacitor), overvoltage protection (OVP pin at 1.24V), thermal shutdown (150°C), and fault flag output (FF pin pulled low during faults). All protections are hardware-based and require no MCU intervention.

Is MP3391EF-LF-Z compatible with both PWM and analog dimming inputs?

Yes. It supports two independent dimming methods: (1) external PWM signal applied to DBRT pin (0–5V, 100Hz–20kHz), and (2) DC voltage (0.2–1.2V) on DBRT with internal DPWM generation timed by BOSC capacitor. Both methods modulate all 8 channels synchronously with no inter-channel phase shift.

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 (e.g., output short to ground or device disable). When active, it turns on an external high-side PMOS to isolate VIN from the rest of the system - enhancing safety and enabling hot-swap capability in modular backlight designs.

Does MP3391EF-LF-Z require external compensation components?

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