Monolithic Power Systems Inc. MP3378GY-Z

Overview

MP3378GY-Z from Monolithic Power Systems is a dual-function integrated WLED backlight controller and synchronous buck converter for LCD monitor power systems. It delivers 4-channel, up to 350 mA/string constant-current LED driving with 2.5% current matching accuracy, plus a 5 V/6 A buck regulator with 144 mΩ/58 mΩ internal MOSFETs, operating from 5–24 V input. Used in desktop flat-panel displays to simultaneously power LED backlights and internal logic rails.

For engineers reviewing the MP3378GY-Z datasheet, MP3378GY-Z pinout, MP3378GY-Z application, or MP3378GY-Z equivalent, key selection criteria include independent PWM/analog dimming per string, OVP/short/open LED protection, thermal shutdown with 25°C hysteresis, and synchronization capability from 250 kHz to 2 MHz.

Technical Context

The MP3378GY-Z integrates two independent switching regulators: a peak-current-mode boost controller for WLED strings (programmable 150–590 kHz via OSC resistor) and a fixed-frequency (235 kHz typ.) current-mode buck converter with AAM light-load mode. Both sections feature dedicated ground pins (GND1/GND2), separate bias supplies (VCC1/VCC2), and isolated feedback paths (COMP/FB).

It implements multi-level protection including cycle-by-cycle ISENSE current limiting (230 mV threshold), recoverable thermal shutdown at 150°C, LED open/short detection via LEDX pins and OVP pin, and inductor/diode short latching after 512 cycles. Dimming control supports simultaneous analog (ADIM, 0.41–1.49 V linear range) and PWM (PWM pin, >20 kHz recommended) inputs.

Key Specifications

Pinout & Package

MP3378GY-Z is housed in a 28-pin SOIC package with exposed thermal pad (connected to GND). Pin numbering follows standard SOIC top-view layout with pin 1 at bottom-left corner.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP3378GY-Z, MPQ3378-AEC1 adds automotive compliance but increases cost and footprint; RT8570GSP reduces integration and current capability, requiring additional components and limiting display brightness scalability.

Availability

MP3378GY-Z 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 MP3378GY-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 design centers in the US, China, and Taiwan.

The MP3378 product line targets cost-optimized, high-reliability LCD backlight power solutions for consumer and industrial displays, integrating WLED control and buck conversion to reduce system complexity.

FAQ

What is the maximum total LED current supported by MP3378GY-Z?

The MP3378GY-Z supports up to 350 mA per string across 4 independent channels, enabling a maximum total LED current of 1.4 A. Each channel regulates current via its own ISET resistor, and current matching remains within ±2.5% across all strings under full load and temperature variation.

Can MP3378GY-Z drive LEDs directly without an external MOSFET?

No. The MP3378GY-Z does not integrate high-voltage power switches for the boost stage. Pins LED1–LED4 are open-drain current sinks that require connection to the cathodes of externally driven LED strings, while GATE drives an external N-channel MOSFET to complete the boost converter topology.

How does the AAM mode improve light-load efficiency?

AAM (Advanced Asynchronous Modulation) disables the internal clock when load demand drops below a threshold set by the AAM pin voltage. This forces pulse-skipping operation, reducing switching losses and quiescent current (IQ2 = 200 μA typ.), thereby improving efficiency at loads below ~20% of full scale without requiring external control signals.

What is the purpose of separate GND1 and GND2 pins?

GND1 serves as the return path for the WLED boost section, while GND2 handles the buck converter and analog ground (AGND). Separating these grounds minimizes noise coupling between high-current boost switching and sensitive buck feedback, preserving regulation accuracy and EMI performance in mixed-signal display power systems.

Does MP3378GY-Z support synchronization of both boost and buck sections?

Only the buck converter supports external synchronization via the SYNC pin (250 kHz to 2 MHz range). The boost section uses a resistor-programmed oscillator (OSC pin) and cannot be synchronized externally. This allows system-level clock alignment for the buck rail while maintaining independent, optimized frequency for the WLED driver.

How is LED open-string fault detected and handled?

Open-string detection occurs when an LEDX pin voltage falls below 190 mV. After OVP threshold (1.23 V) is exceeded for >4 µs, the controller marks off the faulty string and continues regulating remaining strings. All strings open triggers full shutdown until EN is cycled, preventing uncontrolled voltage rise and ensuring safe failure mode.

What thermal derating applies to the SOIC-28 package at 85°C ambient?

With θJA = 62.5°C/W, the maximum allowable power dissipation at 85°C ambient is PD(MAX) = (150°C − 85°C) / 62.5°C/W = 1.04 W. This limits continuous operation to ~65% of the 2 W rating at 25°C, requiring careful layout and airflow consideration in thermally constrained monitor enclosures.