Monolithic Power Systems Inc. MP3391EY-LF-Z

Overview

MP3391EY-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 MP3391EY-LF-Z datasheet, MP3391EY-LF-Z pinout, MP3391EY-LF-Z application, or MP3391EY-LF-Z equivalent, key selection considerations include its 8-string current-source architecture, 450mV LED regulation voltage, VFAULT-controlled PMOS disconnect, open/short LED protection with TSET/SSET programming, and SOIC-28 package thermal performance (θJA = 60°C/W).

Technical Context

The MP3391EY-LF-Z implements a peak-current-mode boost converter with internal 10V VDD and 5V VCC linear regulators-VDD powers the gate driver, VCC supplies control logic. Its 8-channel current sources operate as open-drain outputs (LED1–LED8), each regulated to match within ±2.5% at up to 120mA, with 450mV compliance voltage minimizing conduction loss.

Protection is fully configurable: OVP threshold set via resistor divider on pin 22 (1.24V reference), short-LED detection via SSET pin (4.5×Vsset threshold), fault timing via TSET capacitor (1.24V trip), and fault flag output on FF (open-drain N-MOS). Dimming supports external PWM on DBRT or internal DPWM generated from BOSC capacitor with DC input on DBRT.

Key Specifications

Pinout & Package

MP3391EY-LF-Z is housed in a 28-pin SOIC package (body width 7.5mm, JEDEC MS-012), rated for -20°C to +85°C ambient operation, with θJA = 60°C/W and θJC = 30°C/W on 4-layer PCB.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MPQ3391-AEC1, MP3391EY-LF-Z trades automotive qualification for lower cost and simplified qualification path in industrial/commercial displays; versus LM3409QMY/NOPB, it delivers true plug-and-play 8-string regulation without external matching circuitry or fault-handling complexity.

Availability

MP3391EY-LF-Z is available at Aetrix Electronics and suitable for LCD TV backlighting, professional monitor systems, desktop flat-panel displays, and commercial video signage requiring stable component supply across long production cycles.

Supply support for MP3391EY-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 solutions.

The MP3391 product line targets large-format LCD backlighting applications, emphasizing precision current matching, robust fault protection, and flexible dimming-designed specifically for display manufacturers needing reliable, scalable WLED control.

FAQ

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

The MP3391EY-LF-Z supports up to 8 independent LED strings simultaneously. The actual count (8, 6, or 4) is selected dynamically via the NUMSEL pin: floating enables all 8 channels (LED1–LED8), high logic enables 6 (LED1–LED6), and low logic enables 4 (LED1–LED4). This configuration is hardwired at startup and does not require register programming.

How is LED current accuracy achieved across channels?

MP3391EY-LF-Z achieves ±2.5% current matching between strings using matched internal current sources and a shared 1.23V ISET reference. Each LEDX pin operates as a precision current sink with 450mV compliance voltage, minimizing process- and temperature-induced mismatches. No external calibration or trimming is required to meet this specification under recommended operating conditions.

Can MP3391EY-LF-Z drive LEDs directly without an external MOSFET?

No. MP3391EY-LF-Z is a controller-only IC and requires an external N-channel power MOSFET connected to the GATE pin. It provides 10V gate drive capability (4.5Ω source / 1.5Ω sink) but contains no integrated power switch. The external MOSFET handles the main boost converter switching current, while MP3391EY-LF-Z manages regulation, protection, and dimming logic.

What protection features are configurable via external components?

Three key protections are externally programmable: Over-voltage protection (OVP) via resistor divider on pin 22 (1.24V threshold), short-LED detection voltage via SSET pin (4.5×Vsset), and short-LED timeout via TSET capacitor (1.24V trip point, t = 0.0248 × C in ms). Open-string detection is automatic and does not require external components beyond the OVP divider.

Is thermal shutdown integrated, and what is its threshold?

Yes, MP3391EY-LF-Z includes internal thermal shutdown with a fixed 150°C junction threshold. When die temperature exceeds this value, the device disables the step-up converter and all LED current sources while maintaining VCC/VDD regulation. Recovery occurs automatically once junction temperature falls below hysteresis (typically ~140°C), with no latch or external reset required.

Does MP3391EY-LF-Z support analog dimming?

It supports DC-input PWM dimming-not true analog dimming. Applying a 0.2–1.2V DC voltage to the DBRT pin linearly controls internal DPWM duty cycle (0–100%), while BOSC capacitor sets the DPWM frequency. This produces pulse-width-modulated LED current, preserving color fidelity and avoiding low-frequency flicker associated with analog current reduction.

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

VFAULT is a dedicated driver output for an external high-side PMOS transistor. During normal operation, it turns on the PMOS to connect input to the boost stage. Upon open/short LED fault detection, it turns off the PMOS to isolate the input supply from the faulty output, preventing bus collapse and enabling safe system-level fault containment without requiring additional control logic.