Monolithic Power Systems Inc. MP3393EF-LF

Overview

MP3393EF-LF from Monolithic Power Systems is an 8-string white LED step-up controller IC designed for large-panel LCD backlighting. It drives external NMOS and PNP transistors, supports 9–32V input, delivers up to 300mA per string with 1.2% current matching accuracy, and features programmable 120–160kHz switching frequency via OSC pin resistor. Used in LCD TVs and monitors requiring precise multi-string current regulation.

For engineers reviewing the MP3393EF-LF datasheet, MP3393EF-LF pinout, MP3393EF-LF application, or MP3393EF-LF equivalent, key selection criteria include its external transistor control architecture, 202mV FB regulation voltage, daisy-chain capability for >8 strings, OVP/short/open protection logic, and TSSOP28EP thermal performance (θJA = 32°C/W).

Technical Context

The MP3393EF-LF implements peak-current-mode step-up control with internal 10V LDO (VCC) powering gate drivers and analog circuitry. Its error amplifier compares 320mV CTLx reference against feedback to regulate external PNP base drive, while ISENSE enables cycle-by-cycle inductor current limiting.

It integrates dual-protection arbitration: open-string detection via CTLx UVLO (210mV threshold) and short-string detection via CTLx OV (6.4V threshold), both triggering FF flag assertion and VFAULT-controlled PMOS disconnect. Daisy-chaining uses shared COMP and synchronized EN/DIM signals across multiple ICs.

Key Specifications

Pinout & Package

MP3393EF-LF is housed in a thermally enhanced TSSOP28EP package with exposed pad tied to GND for improved heat dissipation (θJA = 32°C/W). The 28-pin layout supports high-density LED driver PCBs with dedicated FB/CTL pairs per string and system-level fault signaling.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8-channel WLED step-up controller applications.

Compared with MP3393EF-LF, MPQ3393-AEC1 adds automotive qualification without altering functionality, while RTQ2133B-QA trades external FET flexibility and 8-string capability for integration and lower voltage rating - making MP3393EF-LF optimal for scalable, high-voltage industrial LCD backlights.

Availability

MP3393EF-LF is available at Aetrix Electronics and suitable for LCD TV backlight systems, commercial monitor lighting, and medical imaging displays requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MP3393EF-LF 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 MP3393 product line targets large-format LCD backlighting applications, delivering high-accuracy multi-string current regulation with robust fault protection and thermal management for consumer and industrial displays.

FAQ

What is the minimum recommended current-sense resistor value for 300mA LED string current?

The MP3393EF-LF regulates string current using a 202mV FB reference. For 300mA, R_SET = 202mV / 0.3A = 0.673Ω. A standard 0.68Ω, 1% tolerance, 1W metal film resistor meets thermal and accuracy requirements while ensuring stable operation across temperature.

How does the MP3393EF-LF handle a single open LED string during operation?

When one string opens, its CTLx pin voltage drops below 210mV, triggering open-string detection. The IC disables that channel while maintaining regulation on remaining strings using the highest-voltage active CTLx as feedback reference. FF pin asserts low, and VFAULT disconnects input only if all strings fail.

Can the MP3393EF-LF be used without an external boost MOSFET?

No. The MP3393EF-LF is a controller-only IC with no integrated power switch. It requires an external NMOS (driven by GATE) and external PNP transistors (driven by CTLx pins) to regulate LED current. Omitting either violates functional architecture and will prevent operation.

What is the purpose of the ISENSE pin, and how should it be connected in a single-IC design?

ISENSE monitors inductor peak current for cycle-by-cycle limiting. In a standalone MP3393EF-LF design (not daisy-chained), ISENSE must be tied directly to GND. Leaving it floating causes undefined behavior and potential overcurrent damage to the external MOSFET.

Does the MP3393EF-LF support synchronization of switching frequency between multiple ICs?

No. The MP3393EF-LF lacks a clock sync input. When daisy-chained, each IC operates at its own independently set frequency (via individual ROSC resistors). Synchronization requires external clock injection or use of a master-slave oscillator scheme outside the IC's native capability.

What is the maximum allowable continuous LED string current per channel?

The MP3393EF-LF supports up to 300mA per string under recommended operating conditions (T_J ≤ 125°C, proper thermal layout). While the datasheet notes "maximum channel current over 350mA", this is a transient capability - sustained operation above 300mA requires derating based on θJA, ambient temperature, and PCB copper area.

How does the OVP pin function during normal operation versus fault condition?

During normal operation, the OVP pin monitors a resistor divider from the boost output; its voltage remains below 1.23V. If an open string causes output overvoltage, OVP pin voltage reaches 1.23V, triggering OVP mode: GATE turns off, FF pulls low, and VFAULT disconnects input via external PMOS within microseconds.