Monolithic Power Systems Inc. MP3378GY

Overview

MP3378GY from Monolithic Power Systems is a dual-function IC integrating a 4-channel WLED boost controller and a synchronous buck converter in one SOIC-28 package. It delivers up to 350 mA per LED string with 2.5% current matching accuracy, supports independent PWM/analog dimming, and provides a regulated 5 V output from 5–24 V input for internal bus or standby power-used in LCD monitor backlighting systems.

For engineers reviewing the MP3378GY datasheet, MP3378GY pinout, MP3378GY application, or MP3378GY equivalent, this device is selected for high-accuracy multi-string LED current regulation, integrated protection (OVP/OTP/LED open-short), and compact power conversion where space-constrained display designs require co-located backlight and auxiliary rail generation.

Technical Context

The WLED controller employs peak-current-mode step-up topology with programmable switching frequency (150–590 kHz) and internal 6 V LDO (VCC1) for gate drive. It uses four open-drain LEDX outputs to sink current from external MOSFET-driven strings and monitors OVP, ISENSE, and LEDX voltages for fault detection including latch-off after 4096 cycles on short-string events.

The buck converter operates in fixed-frequency (235 kHz typ.) current-mode control with integrated 144 mΩ/58 mΩ HS/LS MOSFETs, AAM light-load mode, and sync capability up to 2 MHz. Its FB pin references an internal 791 mV threshold, and thermal shutdown activates at 150°C with 25°C hysteresis.

Key Specifications

Pinout & Package

MP3378GY is housed in a 28-pin SOIC package with exposed thermal pad connected to GND. Pin numbering follows standard SOIC top-view layout with GND1 (Pin 1), GND2 (Pins 17–18), and AGND (Pin 19) providing separate ground domains for WLED and buck sections to minimize noise coupling.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MPQ3378GQ-A, the MP3378GY offers identical functionality at lower cost and smaller footprint but lacks automotive qualification; versus RT8585GSP, it reduces component count and improves current matching at the expense of vendor lock-in and less granular control over individual converters.

Availability

MP3378GY is available at Aetrix Electronics and suitable for desktop LCD flat panel displays, flat panel video displays, and 2D/3D LCD TVs and monitors requiring stable component supply, consistent parametric performance, and long-term production continuity.

Supply support for MP3378GY 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 MP3378 belongs to MPS's WLED backlight controller product line, designed specifically for space-constrained, high-reliability display applications demanding integrated boost + buck functionality and robust fault protection.

FAQ

What is the maximum LED string voltage the MP3378GY can support?

The MP3378GY supports up to 55 V on each LEDX pin (VLED1–VLED4), enabling configurations with up to 15–18 white LEDs per string at typical forward voltage (3.0–3.4 V). The actual maximum string voltage depends on external MOSFET breakdown rating and Schottky diode selection, but the IC's OVP threshold is programmable up to 6.8 V to prevent overvoltage damage.

Can the MP3378GY operate with only the buck converter enabled while disabling the WLED controller?

Yes. The WLED controller is disabled by pulling EN low (≤0.6 V), which shuts down GATE, OSC, COMP, and all LEDX outputs while leaving the buck converter fully operational. VIN2, FB, and AAM remain functional, allowing independent use of the 5 V buck rail for system logic or peripherals without WLED activity.

How does the MP3378GY handle LED string mismatch during open-circuit faults?

When an LED string opens, its corresponding LEDX pin voltage drops below 190 mV. After detecting this condition for >4 µs, the MP3378GY marks off that string and continues regulating remaining strings using the highest LEDX voltage as the reference. This maintains stable output voltage and prevents overvoltage on functional strings.

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

The datasheet specifies L2 = 10 µH in the typical application circuit. For 5 V output at 235 kHz, the minimum practical inductance is 6.8 µH to maintain CCM operation above 200 mA load and avoid excessive peak current ripple. Lower values increase conduction losses and may trigger current-limit protection under heavy load.

Is the MP3378GY RoHS-compliant and halogen-free?

Yes. All MP3378 variants-including MP3378GY-are lead-free, halogen-free, and fully compliant with the EU RoHS directive. MPS confirms green status on its official website under Quality Assurance documentation, with full material declarations available upon request.

Does the MP3378GY support daisy-chained synchronization across multiple ICs?

No. The SYNC pin accepts only a single external clock source and does not provide an output clock signal. Multiple MP3378GY devices can be synchronized to the same master clock, but they cannot be cascaded or daisy-chained-the SYNC input is receive-only with no buffered output or fan-out capability.

What is the purpose of the NC pins (10 and 11) on the MP3378GY?

Pins 10 and 11 are no-connect (NC) terminals-internally unconnected and electrically isolated. They must remain unconnected in PCB layout; routing traces or placing vias on these pads may cause mechanical stress or unintended coupling. Their presence accommodates package die size and pinout standardization across the MP33xx family.