Monolithic Power Systems Inc. MP3394SGS

Overview

MP3394SGS from Monolithic Power Systems is a 4-string, step-up white LED driver IC designed for large LCD panel backlighting. It operates from 5V–28V input, delivers up to 200mA per string with 2.5% current matching accuracy, and uses external MOSFET control with programmable switching frequency (140–670 kHz) for efficient boost conversion in flat-panel TV and monitor applications.

For engineers reviewing the MP3394SGS datasheet, MP3394SGS pinout, MP3394SGS application, or MP3394SGS equivalent, this device supports dual dimming modes (external PWM and DC-input burst PWM), open/short LED protection, cascading for 8+ strings, and OVP programming - critical for robust backlight power management in high-reliability display systems.

Technical Context

The MP3394SGS employs peak-current-mode control with fixed-frequency operation, where switching frequency is set via an external resistor on the OSC pin (140–670 kHz). Its internal 5.8V LDO powers gate drive and logic, and UVLO (3.5–4.4 V) ensures safe startup.

Four matched current sinks (LED1–LED4) regulate string current using an ISET-resistor–based reference (1.22 V typical), achieving ±2.5% inter-string matching. Dimming is implemented either by external PWM on DBRT or DC voltage (0.2–1.2 V) with BOSC capacitor–set internal oscillator (1–2 kHz).

Key Specifications

Pinout & Package

MP3394SGS is packaged in SOIC16 with exposed pad (no thermal pad connection required per datasheet); pin functions are validated per MPS Rev. 1.03 datasheet (2013). Pin numbering follows standard SOIC16 top-view orientation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 4-string WLED driver applications.

Compared with MP3394SGS, MPQ3367-AEC1 trades programmability and cascading for automotive reliability and integration, while LM3409QMY requires significant external circuitry to emulate even basic 4-string functionality - making MP3394SGS the optimal choice for scalable, high-accuracy LCD backlight systems.

Availability

MP3394SGS is available at Aetrix Electronics and suitable for desktop LCD flat panels, flat-panel video displays, and 2D/3D LCD TVs requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for MP3394SGS 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 MP3394S product line targets large-format LCD backlighting, delivering high-efficiency, multi-string LED current regulation with integrated protection and flexible dimming - optimized for cost-sensitive, high-volume display manufacturing.

FAQ

What is the maximum allowable LED string voltage when using MP3394SGS without external MOSFETs?

The LED1–LED4 pins tolerate up to 6.1 V (per absolute max rating). If string forward voltage exceeds this - e.g., >10 WLEDs @ 3.2 V each = 32 V - external N-MOSFETs must be added per channel to protect the IC. Datasheet Figure 8 shows the required configuration with gate drive from GATE pin.

Can MP3394SGS operate with input voltage below 5 V?

No. The absolute minimum VIN is 5 V per datasheet Recommended Operating Conditions, and UVLO rising threshold is 3.5–4.4 V - but guaranteed operation starts only at 5 V. Below that, regulation fails, VCC drops, and gate drive collapses. Use a pre-regulator if 3.3 V or battery-derived inputs are required.

How does open-string protection behave when only one LED string opens?

The IC detects low voltage (<196 mV) on the affected LEDX pin, marks that string OFF, and continues regulating remaining strings at full current. Output voltage self-adjusts to the highest-voltage active string, preserving partial backlight function - confirmed in Typical Performance Characteristic "Open one LED string at working" on page 5.

What is the minimum recommended DBRT PWM signal amplitude for reliable dimming?

The datasheet specifies ≥1.2 V for high level and ≤0.4 V for low level. Amplitudes below 1.2 V may cause incomplete turn-on; signals above 0.4 V in low state result in residual conduction and reduced dimming range - verified in Figure 4 and Table 1 (Direct PWM Dimming).

Is thermal derating required for SOIC16 package at 125°C ambient?

Yes. With θ_JA = 80 °C/W and T_J(MAX) = 150 °C, maximum allowed power dissipation at 125°C ambient is (150 − 125)/80 = 0.3125 W. At full 4 × 200 mA load, typical power loss exceeds this - forced airflow or PCB copper area enhancement is mandatory per thermal design guidelines on page 2.

Does MP3394SGS support I²C or analog voltage dimming directly?

No. It supports only two hardware-based methods: external PWM signal on DBRT (with BOSC grounded via resistor), or DC voltage (0.2–1.2 V) on DBRT with BOSC capacitor. No digital interface or DAC input is integrated - dimming control must be implemented externally via MCU GPIO or analog circuitry.

What happens to COMP voltage during thermal shutdown?

During thermal shutdown, the error amplifier is disabled and COMP discharges through its external capacitor. The voltage collapses to near 0 V, halting switching activity. Recovery requires EN toggling or ambient cooling below T_ST − hysteresis (≈145°C), after which soft-start reinitiates regulation - described in Operation section on page 9.