Monolithic Power Systems Inc. MP3378GF-P

Overview

MP3378GF-P from Monolithic Power Systems is a dual-function integrated WLED backlight controller and synchronous buck converter for LCD monitor power systems. It integrates a 4-string, 350 mA/channel boost LED driver with independent PWM/analog dimming control and a high-efficiency buck regulator featuring 144 mΩ/58 mΩ internal MOSFETs, 235 kHz fixed switching frequency, and AAM light-load mode. It operates across 5–24 V input and delivers stable bus voltage or standby power in desktop flat-panel displays.

For engineers reviewing the MP3378GF-P datasheet, MP3378GF-P pinout, MP3378GF-P application, or MP3378GF-P equivalent, key selection considerations include its dual-regulator architecture, 2.5% LED current matching accuracy, OVP/OTP/UVP/short-circuit protections, TSSOP-28EP thermal performance (θJA = 32°C/W), and compatibility with external MOSFET gate drive for high-voltage LED strings.

Technical Context

The MP3378GF-P implements two independent switching regulators on a single die: a peak-current-mode step-up controller for LED string biasing and a current-mode synchronous buck converter for system rail generation. The WLED section uses programmable oscillator frequency (via OSC pin resistor), cycle-by-cycle ISENSE current limiting (145–230 mV threshold), and open/short LED detection via dedicated LED1–LED4 pins and OVP monitoring.

The buck section employs fixed-frequency (235 kHz) operation with external SYNC capability (250 kHz–2 MHz), AAM mode for PFM light-load efficiency, and internal soft-start (1.5 ms). Its feedback loop references a precision 791 mV FB voltage, while protection includes hiccup-mode OCP, thermal shutdown at 150°C, and VIN2 UVLO with 3.9 V rising threshold and 650 mV hysteresis.

Key Specifications

Pinout & Package

TSSOP-28EP package with exposed thermal pad (connected to GND); 0.65 mm pitch, 9.7 mm × 4.4 mm body size; θJA = 32°C/W on 4-layer PCB.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar WLED controller plus buck converter applications.

Compared with MP3378GF-P, MPQ3378-AEC1 adds automotive reliability at higher cost and complexity, while RT8570GQW lacks integrated buck functionality - making MP3378GF-P the optimal choice for space-constrained, dual-rail LCD monitor designs requiring single-chip integration and industrial-grade robustness.

Availability

MP3378GF-P is available at Aetrix Electronics and suitable for desktop LCD monitors, flat-panel video displays, 2D/3D LCD TVs, and industrial control panels requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MP3378GF-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 mixed-signal ICs for power management, motor drive, and automotive applications.

The MP3378 product line targets LCD backlight power solutions, integrating WLED control and system rail generation into compact packages to reduce design complexity and improve thermal performance in space-constrained displays.

FAQ

What is the maximum input voltage supported by MP3378GF-P?

The MP3378GF-P supports up to 24 V on both VIN1 (WLED controller) and VIN2 (buck converter) inputs. Absolute maximum ratings specify –0.3 V to +28 V for VIN1 and VIN2, but recommended operating conditions limit continuous operation to 5–24 V to ensure reliability and thermal stability within the TSSOP-28EP package's 3.9 W power dissipation limit.

How does the MP3378GF-P handle LED string failures?

It detects open strings via LEDX pin voltage monitoring and OVP threshold violation (>4 µs above 1.23 V), then disables affected channels while maintaining regulation on remaining strings. For shorted strings, it identifies voltages >6.3 V on LEDX pins and marks them off after 4096 switching cycles, isolating faults without full shutdown.

Can the buck converter output voltage be adjusted below 0.8 V?

No. The internal reference voltage is fixed at 791 mV ±12 mV, and the FB pin is designed for resistive divider feedback. Output voltage is calculated as V_OUT = 0.791 V × (1 + R1/R2), with minimum practical output constrained by reference accuracy and noise margin - typically not usable below 0.8 V.

What is the purpose of the AAM pin and how is it configured?

The AAM pin sets the threshold for asynchronous modulation mode. Connecting a resistor from AAM to GND establishes a voltage that determines the light-load transition point: when COMP_BUCK falls below VAAM and FB < VREF, the controller enters PFM mode, skipping pulses to maintain efficiency down to ~50 mA load.

Is thermal pad connection mandatory for MP3378GF-P?

Yes. The exposed pad in the TSSOP-28EP package must be soldered to a solid GND copper plane. Thermal resistance data (θJC = 6°C/W) assumes direct pad-to-PCB conduction; omitting this connection degrades θJA from 32°C/W to >60°C/W, risking thermal shutdown under 2 A buck load or 350 mA/string WLED operation.

Does MP3378GF-P support synchronization between boost and buck switching frequencies?

No. The boost section uses independent OSC pin programming (150–590 kHz), while the buck section accepts external SYNC signals (250 kHz–2 MHz) only on its dedicated SYNC pin. There is no internal coupling or phase alignment between the two regulators' switching events.

What is the minimum recommended inductor value for the buck converter?

Based on 235 kHz switching frequency and 7.2 A current limit, the minimum recommended inductance is 10 µH (as shown in the typical application circuit). Using lower values risks peak current exceeding ILIMIT, triggering hiccup-mode OCP and reducing output voltage regulation accuracy under transient loads.