Monolithic Power Systems Inc. MP3378EGF

Overview

MP3378EGF from Monolithic Power Systems is a dual-function integrated WLED backlight controller and buck converter IC for LCD monitor power systems. It integrates a 4-string, up to 350mA/string boost LED driver with independent analog/PWM dimming and a synchronous buck converter delivering adjustable output (0.8V–5V) with 144mΩ/80mΩ internal MOSFETs. Designed for desktop flat-panel displays, it operates across 5–24V input, delivers 2.5% current matching accuracy, and includes full protection suites for both sections.

For engineers reviewing the MP3378EGF datasheet, MP3378EGF pinout, MP3378EGF application, or MP3378EGF equivalent, key selection considerations include its dual-rail operation (VIN1/VIN2), independent enable controls (EN1/EN2), TSSOP-28 EP thermal performance (θJA = 32°C/W), and compatibility with external MOSFET gate drive (GATE) and current-sense (ISENSE) topologies in high-reliability display power designs.

Technical Context

The MP3378EGF implements two independent switching regulators on a single die: a peak-current-mode step-up WLED controller with programmable frequency (150–590 kHz) and four open-drain LEDX outputs for string current regulation, plus a fixed-frequency (235 kHz typ.) current-mode buck converter with internal high-side/low-side MOSFETs and SYNC capability (250 kHz–2 MHz). Both sections feature dedicated error amplifiers (COMP, FB), soft-start, and cycle-by-cycle current limiting.

Its architecture supports system-level coordination: the WLED controller uses VCC1 (6V LDO) for gate drive and internal logic, while the buck supplies VCC2 (4.9V) and powers auxiliary circuitry; OVP threshold is set via external resistor divider on OVP pin, and LED string health is monitored via individual LED1–LED4 pins with open/short detection thresholds (190 mV UVLO, 6.3 V OV).

Key Specifications

Pinout & Package

The MP3378EGF is housed in a thermally enhanced TSSOP-28 EP package with exposed pad tied to GND1/GND2 for improved heat dissipation (θJC = 6°C/W). Pin functions are electrically segregated: WLED section (pins 1–11, 22–28) and buck section (pins 12–21) share ground planes but maintain independent power domains and control paths.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-rail LED backlight controller applications.

Compared with MPQ3378-AEC1, the MP3378EGF offers identical functionality at lower cost and qualification overhead for industrial/commercial use; versus RT8542GSP, it reduces total solution size and component count by integrating both WLED control and buck conversion in one TSSOP-28 EP package.

Availability

MP3378EGF is available at Aetrix Electronics and suitable for desktop LCD flat panel displays, flat panel video displays, and industrial control panel displays requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MP3378EGF 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, and global distribution through authorized partners.

The MP3378EGF belongs to MPS's display power management product line, engineered specifically for integrated backlight and system rail solutions in space-constrained LCD monitor and TV applications.

FAQ

What is the maximum recommended LED string voltage for MP3378EGF?

The MP3378EGF supports up to 55V on LED1–LED4 pins, enabling configurations with up to 15–18 white LEDs per string (assuming 3.0–3.3V forward voltage). The actual maximum string voltage depends on the programmed OVP threshold, which is set externally via resistor divider on the OVP pin and defaults to ~6.3V above the LED cathode voltage.

Can MP3378EGF operate with only the buck converter enabled while the WLED controller is disabled?

Yes. The WLED controller (EN1) and buck converter (EN2) have independent enable inputs. With EN1 = 0V and EN2 = 5V, the buck section operates normally - delivering regulated output from VIN2, powering VCC2, and supporting SYNC and FB feedback - while the WLED section remains fully inactive and draws only 1μA shutdown current.

How does the MP3378EGF handle LED string open-circuit faults?

When an LED string opens, its corresponding LEDX pin voltage drops below 190mV. After >4µs of OVP threshold violation, the controller marks that string as faulty and disables it. Remaining active strings continue regulation, and the output voltage adjusts to the highest-voltage string's requirement. All four strings open triggers full shutdown until reset via EN1 toggle.

What is the purpose of the ISENSE pin and how is it used in the WLED controller?

The ISENSE pin senses voltage across an external current-sense resistor placed between the boost inductor and GND1. It provides real-time inductor current feedback for peak-current-mode control and cycle-by-cycle overcurrent limiting. During normal operation, it sets the MOSFET on-time; during fault conditions, it triggers latching shutdown if sensed voltage exceeds 660mV for four consecutive cycles.

Is external compensation required for stable operation of the MP3378EGF buck converter?

No external compensation is required for the buck converter's internal error amplifier - MPS has optimized the compensation network for standard 10µH inductors and ceramic output capacitors. However, the WLED controller's COMP pin requires an external RC network (resistor + capacitor in series to GND) to stabilize the boost loop; values depend on selected inductor, output capacitance, and desired phase margin.

Does MP3378EGF support dimming synchronization across multiple ICs in a large display?

The MP3378EGF does not provide master/slave dimming sync. While its buck section supports clock synchronization via the SYNC pin, the WLED controller's PWM and ADIM inputs are independent per device. For synchronized dimming across multiple MP3378EGFs, a common PWM signal must be distributed externally to all PWM pins, with careful attention to trace length matching and noise immunity.