Monolithic Power Systems Inc. MP3378EGF-Z

Overview

MP3378EGF-Z from Monolithic Power Systems is a dual-function LED backlight controller IC integrating a 4-channel WLED boost controller and a synchronous buck converter in one TSSOP-28 EP package. It delivers up to 350mA per string with 2.5% current matching accuracy, supports independent analog/PWM dimming, and provides integrated OCP, OVP, OTP, LED open/short, and inductor/diode short protection. It is designed for desktop LCD monitors requiring stable 5V auxiliary rail generation and precise multi-string LED current regulation.

For engineers reviewing the MP3378EGF-Z datasheet, MP3378EGF-Z pinout, MP3378EGF-Z application, or MP3378EGF-Z equivalent, key selection considerations include its dual-regulator architecture (boost + buck), 4-string independent dimming capability, 235kHz fixed/250kHz–2MHz syncable buck frequency, 144mΩ/80mΩ internal MOSFET R_DS(ON), and thermal shutdown with 25°C hysteresis - all critical for monitor backlight and system power co-design.

Technical Context

The MP3378EGF-Z implements two independent switching regulators: a peak-current-mode step-up WLED controller with programmable 150–590kHz frequency (via OSC resistor) and a fixed-frequency (235kHz typ.) or externally synchronized (250kHz–2MHz) current-mode buck converter. Each regulator features dedicated enable inputs (EN1/EN2), separate ground domains (GND1/GND2), and isolated feedback paths (COMP/FB).

Its WLED section uses open-drain LEDx outputs driving external high-side N-MOSFETs, with ISET-regulated 1.225V reference enabling precise current setting via external resistor; the buck section integrates 144mΩ HS and 80mΩ LS MOSFETs, 0.791V FB reference, and hiccup-mode OCP triggered when FB drops below 400mV during fault conditions.

Key Specifications

Pinout & Package

TSSOP-28 EP package with exposed thermal pad connected to GND; 28-pin top-view layout includes dedicated WLED (GND1, VIN1, GATE, ISENSE, LED1–LED4, OVP, ISET, ADIM, PWM, COMP, OSC, EN1) and buck (GND2, VIN2, SW, BST, FB, EN2, VCC2, SYNC, AGND) signal groups, plus NC pins (10, 11).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP3378A, MP3378EGF-Z adds SYNC functionality for EMI control and retains identical WLED performance; versus RT8532GQW, it integrates the buck converter to reduce component count and improve system efficiency by eliminating external regulator losses.

Availability

MP3378EGF-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 MP3378EGF-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 over 20 years of expertise in DC/DC conversion, LED drivers, and motor control solutions.

The MP3378 product line targets LCD backlight systems requiring integrated WLED control and auxiliary power generation - designed specifically for monitor and display OEMs needing compact, reliable, and thermally efficient single-chip solutions.

FAQ

What is the maximum LED string voltage supported by MP3378EGF-Z?

The MP3378EGF-Z does not specify a hard maximum string voltage, but its OVP threshold is programmable via the OVP pin with a typical rising-edge threshold of 1.23V and hysteresis of 80mV. When used with a standard resistor divider (e.g., 1MΩ/100kΩ), this allows configuring OVP for output voltages up to ~55V. Absolute maximum rating for VLED1–VLED4 is +55V, confirming safe operation with up to 15–18 white LEDs in series per string at typical forward voltage (3.0–3.3V).

Can MP3378EGF-Z drive LED strings with different numbers of LEDs?

Yes. The MP3378EGF-Z automatically selects the highest active LEDX voltage to regulate the boost output, ensuring sufficient headroom for all strings. If strings have mismatched counts (e.g., 10 vs. 12 LEDs), the controller maintains regulation at the higher-voltage string's requirement. However, current matching remains within 2.5% across all enabled strings, and open-string protection disables any string whose LEDX voltage falls below 190mV - preserving regulation integrity.

How is thermal performance managed in continuous high-load operation?

The MP3378EGF-Z incorporates dual thermal protection: WLED section shuts down at 150°C with 25°C hysteresis, and buck section has identical 150°C shutdown with 20°C hysteresis. Its TSSOP-28 EP package features an exposed pad tied to GND, achieving θ_JA = 32°C/W on a 4-layer PCB. At 25°C ambient, the 3.9W maximum power dissipation allows sustained operation at full 350mA × 4 strings + 5V/2A buck load when PCB copper area and airflow meet JEDEC JESD51-7 guidelines.

Does MP3378EGF-Z support daisy-chained PWM dimming across multiple ICs?

No. MP3378EGF-Z does not include hardware daisy-chain or broadcast PWM synchronization. Each IC requires individual PWM signal routing. However, its SYNC pin enables system-level clock alignment: applying the same external clock to multiple MP3378EGF-Z units (and other compatible MPS devices) ensures switching edges are phase-locked, reducing beat frequencies and improving EMI behavior - a functional alternative to true daisy-chaining for multi-display systems.

What is the minimum inductor value recommended for stable WLED operation?

Stable operation requires inductor selection balancing ripple current, efficiency, and size. With 500kHz switching (ROSC = 115kΩ), the datasheet recommends 10µH for 12V input and 16V output. Minimum on-time is 200ns, so inductor value must ensure peak current does not exceed the 230mV cycle-by-cycle limit (≈7.2A with 33mΩ sense). For 330mA/string, a 4.7µH–10µH shielded power inductor with ≥1.5A saturation current is verified in typical applications - values below 4.7µH risk instability due to insufficient energy storage per cycle.

Is the buck converter output capable of powering the WLED controller's VCC1 supply?

No. VCC1 (6V LDO) is powered exclusively from VIN1 (WLED input rail), not the buck output. The buck converter's VCC2 (5V LDO) powers only its own internal circuitry and external loads connected to VCC2. Attempting to feed VCC1 from the buck output violates absolute maximum ratings: VCC1 must remain ≤6.5V and is internally regulated from VIN1. Using buck output to power VCC1 risks overvoltage damage and invalidates the specified 5V–24V VIN1 operating range.

How does the MP3378EGF-Z handle startup sequencing between WLED and buck sections?

The MP3378EGF-Z requires independent enable sequencing: EN1 must be asserted after VIN1 stabilizes, and EN2 after VIN2 stabilizes. The WLED controller performs topology checks (OVP voltage >75mV) before soft-starting; premature EN1 assertion causes latch-off. Similarly, buck soft-start (1.5ms) begins only after EN2 rises above 1.8V. No internal dependency exists between sections - they operate autonomously, allowing flexible power-up order but requiring external coordination to avoid inrush or undervoltage faults.