Monolithic Power Systems Inc. MP3394EF-LF-P

Overview

MP3394EF-LF-P from Monolithic Power Systems is a step-up white LED driver IC with four independent current-regulated channels, designed for large LCD panel backlighting. It operates from 5V–28V input, delivers up to 200mA per string, achieves ±2.5% inter-string current matching, and uses external MOSFET control with 350mV current-sense voltage for high efficiency in desktop monitors and LCD TVs.

For engineers reviewing the MP3394EF-LF-P datasheet, MP3394EF-LF-P pinout, MP3394EF-LF-P application, or MP3394EF-LF-P equivalent, key selection criteria include programmable switching frequency (145–600 kHz), dual PWM/DC dimming modes, open/short LED protection, OVP threshold programming, and cascading capability for 8+ string configurations.

Technical Context

The MP3394EF-LF-P implements a peak-current-mode, fixed-frequency boost controller with internal 6V LDO (VCC) powering gate drive and logic. Its 4-channel current regulation uses matched internal current sources referenced to a stable 1.23V ISET voltage, enabling 2.5% matching accuracy across strings at 32mA nominal.

Dimming is supported via two distinct paths: external PWM applied to DBRT with BOSC biased by resistor, or DC analog voltage (0.2–1.2V) on DBRT with BOSC capacitor setting internal triangle-wave frequency (1–2 kHz typical). Protection includes programmable OVP (1.23V threshold), LEDX UVLO (196mV), and thermal shutdown at 150°C.

Key Specifications

Pinout & Package

TSSOP16EP package with exposed thermal pad (θJA = 45°C/W, θJC = 10°C/W); RoHS-compliant, lead-free finish.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar WLED backlight driver applications.

Compared with MP3394EF-LF-P, MPQ3394-AEC1 adds automotive reliability at higher cost and identical electrical specs, while LM3409HVMM/NOPB trades integration for topology flexibility-neither offers the same combination of 4-string matching, programmable dimming, and cascading support.

Availability

MP3394EF-LF-P is available at Aetrix Electronics and suitable for desktop LCD monitors, LCD TV backlighting, flat panel video displays, and industrial control panels requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for MP3394EF-LF-P 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 MP3394 belongs to MPS's WLED backlight driver product line, engineered specifically for large-format LCD panel illumination with emphasis on current matching, thermal resilience, and system-level fault management.

FAQ

What is the maximum allowable LED string voltage that MP3394EF-LF-P can regulate?

The MP3394EF-LF-P does not directly regulate string voltage-it regulates current through each string while supporting output voltages up to 55V (per absolute maximum rating for LED pins). The actual usable string voltage depends on external boost components (inductor, diode, capacitor) and input voltage. With 28V input and proper design, outputs exceeding 40V are achievable for 10–12 LED strings in series.

Can MP3394EF-LF-P operate without an external MOSFET?

No. The MP3394EF-LF-P is a controller-only IC and requires an external N-channel MOSFET connected to the GATE pin to implement the step-up converter. It does not integrate a power switch. Attempting operation without the MOSFET will prevent boost functionality and may cause undefined behavior or damage due to uncontrolled voltage rise.

How is current matching accuracy maintained across the four LED strings?

Current matching is achieved using four precision-matched internal current sources referenced to a common 1.23V bandgap voltage at the ISET pin. Each LED string connects to its own open-drain current sink (LED1–LED4), and the IC actively regulates the voltage drop across each sink to maintain 350mV-ensuring ±2.5% matching between strings at 32mA, verified across process, voltage, and temperature.

What happens during an open LED string fault?

When an LED string opens, its corresponding LEDX pin voltage drops below 196mV. The MP3394 detects this condition, marks off the faulty string, and continues regulating the remaining active strings. Output voltage adjusts dynamically to meet the highest-voltage string's requirement. If all four strings open, the device shuts down the boost converter entirely to prevent overvoltage.

Is the TSSOP16EP package thermally enhanced compared to SOIC variants?

Yes. The TSSOP16EP includes an exposed thermal pad that reduces θJA to 45°C/W (vs. 80°C/W for SOIC16), enabling higher continuous power dissipation (2.78W vs. 1.56W at 25°C ambient). This makes it preferred for high-current, high-ambient-temperature applications like enclosed LCD TVs where thermal management is critical.

Does MP3394EF-LF-P support analog dimming?

No. MP3394EF-LF-P supports only PWM-based dimming-either externally applied PWM to DBRT or DC-voltage-controlled internal PWM generation (called "DC input PWM dimming"). There is no true analog (linear) current adjustment; the lowest dimming level is determined by minimum achievable duty cycle (e.g., 0.3% at 100Hz).

How is overvoltage protection configured?

OVP is configured using a resistor divider from the boost output to the OVP pin. When the divided voltage reaches the internal 1.23V threshold, the IC disables the GATE driver. The divider ratio is selected so that OVP triggers at ~1.1–1.2× nominal output voltage-for example, a 1.2× margin on a 40V output sets OVP at 48V using R_HIGH/R_LOW = 38.0.