Monolithic Power Systems Inc. MP3378GF-Z

Overview

MP3378GF-Z from Monolithic Power Systems is a dual-function IC integrating a 4-channel WLED backlight controller and a synchronous buck converter in one SOIC-28EP 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 system bus or standby power in LCD monitor backlighting.

For engineers reviewing the MP3378GF-Z datasheet, MP3378GF-Z pinout, MP3378GF-Z application, or MP3378GF-Z equivalent, this device serves as a complete power + lighting solution for flat-panel displays requiring precise multi-string current regulation, robust fault protection (OVP/OTP/OCP/LED open-short), and compact board space.

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) to drive external N-MOSFETs; it uses ISET-resistor programming (1.225 V reference) and four open-drain LEDX outputs for independent string control. Protection includes recoverable thermal shutdown (150°C), latch-off OVP (1.23 V threshold), and 4096-cycle short-string detection.

The integrated buck converter operates in fixed-frequency (235 kHz typ.) current-mode control with internal 144 mΩ/58 mΩ HS/LS MOSFETs, AAM light-load mode, and adjustable output (0.8 V min) via FB resistor divider; its SYNC pin accepts 250 kHz–2 MHz external clock, and soft-start duration is 1.5 ms typical.

Key Specifications

Pinout & Package

MP3378GF-Z is housed in a thermally enhanced TSSOP-28EP package with exposed pad (connected to GND2) for improved heat dissipation (θJA = 32°C/W). The 28-pin layout separates WLED and buck domains with dedicated ground planes (GND1/GND2/AGND) and isolated power paths.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MPQ3378-AEC1, MP3378GF-Z offers lower cost and smaller footprint but lacks automotive qualification; versus RT4801B, it eliminates external regulator BOM and improves current matching by 2×, enabling tighter brightness uniformity in premium displays.

Availability

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

Supply support for MP3378GF-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 power management ICs, with over 20 years of expertise in DC/DC conversion, LED drivers, and motor control solutions.

The MP3378 product line targets cost-optimized, space-constrained LCD backlight systems - integrating WLED control and system power generation to reduce bill-of-materials and simplify thermal design in consumer and industrial displays.

FAQ

What is the maximum total LED current supported by MP3378GF-Z?

The MP3378GF-Z supports up to 350 mA per string across all four channels, yielding a maximum combined LED current of 1.4 A. Each channel regulates current independently using its own open-drain LEDX output and shares the same ISET reference, ensuring matched performance without inter-channel crosstalk.

Can MP3378GF-Z drive LEDs directly without an external MOSFET?

No. MP3378GF-Z does not integrate high-voltage power switches for the boost stage. Its GATE pin drives an external N-channel MOSFET, and LED1–LED4 are open-drain control outputs - requiring external FETs and Schottky diodes to construct the boost converter. This architecture enables scalability to higher voltages and currents beyond integrated solutions.

How is the buck converter output voltage set?

The buck output voltage is set using a resistor divider from VOUT to AGND, with the midpoint connected to FB. The internal 0.791 V reference determines regulation point: VOUT = 0.791 V × (1 + R1/R2). For example, R1 = 40.2 kΩ and R2 = 7.5 kΩ yields 5.0 V output. FB input bias current is ≤50 nA, minimizing divider error.

Does MP3378GF-Z support synchronization between WLED and buck switching frequencies?

No. The WLED controller's OSC pin sets its own frequency (150–590 kHz) independently, while the buck converter's SYNC pin accepts an external clock (250 kHz–2 MHz) - but there is no internal mechanism to lock or align the two switching frequencies. Designers must manage potential beat frequencies via layout isolation and filtering.

What protection features activate during an LED string open fault?

During an open-string event, the affected LEDX pin voltage drops below 190 mV. After >4 µs, the OVP comparator triggers, and the controller disables that string while maintaining regulation on remaining strings. The output voltage rises until reaching the programmed OVP threshold (e.g., 6.3 V), then latches off if no valid string remains.

Is the TSSOP-28EP package lead-free and RoHS compliant?

Yes. MP3378GF-Z uses a lead-free, halogen-free TSSOP-28EP package fully compliant with EU RoHS Directive 2011/65/EU. The exposed pad is electrically connected to GND2 and must be soldered to a thermal pad on the PCB for optimal thermal performance and mechanical reliability.

What is the minimum recommended input voltage for reliable buck converter startup?

The buck converter requires VIN2 ≥ 3.9 V (rising threshold) to exit UVLO and begin switching. Below this, VCC2 remains unregulated and internal logic is held in reset. For stable operation across temperature and tolerance, design with VIN2 ≥ 4.5 V minimum to ensure margin against dropout and ripple-induced shutdown.