Monolithic Power Systems Inc. MP3399EY-LF-P

Overview

MP3399EY-LF-P from Monolithic Power Systems is a 12-string, cascading white LED driver IC with integrated step-up controller and 12 precision current sources for large LCD panel backlighting. It operates from 5V–28V input, delivers up to 60mA per string, achieves ±2.5% inter-string current matching, and regulates LED current via 1.22V ISET reference with 600mV compliance voltage. Used in high-channel-count TV and monitor backlight systems requiring stable, scalable illumination.

For engineers reviewing the MP3399EY-LF-P datasheet, MP3399EY-LF-P pinout, MP3399EY-LF-P application, or MP3399EY-LF-P equivalent, key selection criteria include cascading capability across multiple ICs using shared inductor topology, programmable switching frequency (150–630 kHz), dual PWM/DC dimming control, open/short LED fault protection, and SOIC-28 thermal performance at +125°C junction temperature.

Technical Context

The MP3399EY-LF-P implements a fixed-frequency, peak-current-mode boost controller driving an external N-MOSFET, with internal 6V LDO (VCC) powering gate drive and logic. Its 12 open-drain LEDX outputs each sink up to 60mA with 2.5% matching accuracy and 600mV regulation voltage, minimizing conduction loss.

Dimming is supported via two modes: external PWM applied to DBRT with BOSC resistor-biased, or DC voltage (0.2–1.2V) on DBRT generating internally synchronized DPWM at frequency set by BOSC capacitor. Protection includes programmable OVP (1.17–1.3V threshold), LEDX UVLO (156–236mV), thermal shutdown at 150°C, and automatic string mark-off for open/short faults.

Key Specifications

Pinout & Package

MP3399EY-LF-P is housed in a RoHS-compliant, lead-free SOIC-28 package (body width 7.5mm, pitch 1.27mm), rated for −40°C to +125°C ambient operation and featuring exposed pad thermal enhancement per MPS datasheet Rev. 1.1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP3399EF-LF-Z, the MP3399EY-LF-P offers lower manufacturing cost and simpler assembly but reduced thermal capability; versus LM3409QMH/NOPB, it delivers plug-and-play 12-string operation with guaranteed matching, eliminating discrete current-source calibration and layout sensitivity.

Availability

MP3399EY-LF-P is available at Aetrix Electronics and suitable for LCD TV backlighting, commercial monitor production, digital signage, and medical imaging displays requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for MP3399EY-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 core expertise in DC/DC conversion, LED drivers, and motor control solutions.

The MP3399 product line targets large-format LCD backlighting applications, emphasizing scalability through cascading, precision current matching, and robust fault protection for mission-critical visual systems.

FAQ

What is the maximum number of MP3399EY-LF-P ICs that can be cascaded?

Multiple MP3399EY-LF-P units can be cascaded in parallel using shared VIN, VCC, COMP, and DBRT connections - the datasheet demonstrates 2-IC (24-string) operation, and designs with ≥3 ICs are feasible with careful layout of shared nodes and grounding. No hard limit is specified, but thermal and PCB routing constraints typically cap practical implementations at 4–6 ICs.

Does MP3399EY-LF-P support analog dimming?

No - MP3399EY-LF-P does not support true analog (linear) dimming. It implements PWM-based brightness control only: either external PWM signal applied to DBRT pin, or DC voltage (0.2–1.2V) converted internally to DPWM. The LED current remains digitally switched; no continuous current adjustment is possible.

Can MP3399EY-LF-P drive LEDs with forward voltage exceeding 28V?

Yes - the boost converter output voltage is not limited to 28V. While VIN range is 5–28V, the regulated output can exceed 100V depending on inductor selection, MOSFET rating, and LED string configuration. The OVP threshold is programmable up to ~60V via the OVP resistor divider, allowing safe operation with high-V_F strings.

What is the purpose of the VFAULT pin?

VFAULT drives an external PMOS transistor to disconnect the input supply from the boost stage during fault conditions (OVP, thermal shutdown, or startup failure). It ramps on/off slowly via external capacitor to control inrush current, and pulls low during normal operation to maintain connection - acting as a controlled power-gate interface rather than a status flag.

Is the ISET pin voltage exactly 1.22V across all operating conditions?

The ISET pin regulates to 1.22V (typ) with ±2.5mV tolerance over temperature and load per datasheet Table 1. This reference is trimmed and stable - deviations beyond ±3mV indicate faulty biasing or excessive leakage. External R_SET must be connected directly to GND; floating or capacitive loading invalidates the current-setting equation.

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

When one string opens, its LEDX pin voltage drops below 180mV; MP3399EY-LF-P marks it off and disables current sinking. Remaining 11 strings continue operation at full current, and the boost output voltage adjusts downward to match the lowest-voltage active string - preserving backlight functionality with only localized dimming loss.

What is the minimum recommended DBRT input voltage for reliable PWM dimming?

For external PWM dimming, the DBRT pin requires ≥1.2V high-level amplitude (per Figure 3) to ensure clean logic-level recognition across temperature and process variation. Voltages below 1.0V may cause inconsistent dimming response or partial channel dropout due to noise margin erosion near the EN threshold.