Monolithic Power Systems Inc. MP3399EY-LF-Z

Overview

MP3399EY-LF-Z from Monolithic Power Systems is a 12-channel, cascading white LED driver IC with integrated step-up controller and 12 matched current sinks 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-brightness TV and monitor backlight systems requiring precise brightness uniformity.

For engineers reviewing the MP3399EY-LF-Z datasheet, MP3399EY-LF-Z pinout, MP3399EY-LF-Z application, or MP3399EY-LF-Z equivalent, key selection criteria include cascading capability across multiple ICs using a shared inductor, programmable 150–630kHz switching frequency, dual-mode PWM/DC dimming control, open/short LED fault protection, and SOIC-28 thermal performance (θJA = 60°C/W).

Technical Context

The MP3399EY-LF-Z implements a peak-current-mode, fixed-frequency boost converter with external MOSFET gate drive (GATE pin), where switching frequency is set by a resistor on OSC (f_SW = 67.85 kΩ / R_OSC). It uses an internal 6V LDO (VCC) to power control circuitry and gate driver, with UVLO activation at 3.9V and 200mV hysteresis.

Twelve open-drain LED current sinks (LED1–LED12) each regulate current via feedback from a common 1.22V ISET reference, achieving 2.5% matching accuracy. Dimming is implemented either by external PWM on DBRT (with BOSC biased by resistor) or DC voltage (0.2–1.2V) on DBRT generating internal DPWM at frequency set by capacitor on BOSC (1.2–2 kHz).

Key Specifications

Pinout & Package

MP3399EY-LF-Z is housed in a RoHS-compliant, lead-free SOIC-28 package (body width 7.5mm, pitch 1.27mm), rated for operation from –40°C to +125°C ambient temperature and featuring θ_JA = 60°C/W on standard 4-layer PCB.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 12-channel WLED driver applications.

Compared with MP3399EF-LF-Z, the MP3399EY-LF-Z offers lower assembly cost and simpler layout in SOIC-28 but trades off thermal performance; versus LM3409QMY/NOPB, it delivers full 12-channel integration, built-in protection, and cascading-reducing design time and component count by >40%.

Availability

MP3399EY-LF-Z is available at Aetrix Electronics and suitable for LCD TV backlighting, professional monitor systems, and commercial flat-panel video displays requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MP3399EY-LF-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 mixed-signal ICs for power management, LED lighting, and motor control applications.

The MP3399 product line is designed specifically for large-format LCD backlighting, emphasizing multi-string current matching, cascading scalability, and robust fault protection in consumer and professional display systems.

FAQ

What is the maximum number of MP3399 ICs that can be cascaded?

Multiple MP3399 ICs can be cascaded in parallel using shared VIN, VCC, and COMP connections - the datasheet demonstrates 2-IC (24-string) operation, and system-level validation confirms reliable extension to ≥4 ICs (48 strings) with proper layout and grounding. No hard limit is specified, but thermal and routing constraints typically cap practical use at 3–4 units per boost stage.

Does MP3399EY-LF-Z support analog dimming?

Yes - the DBRT pin accepts a 0.2V–1.2V DC input to directly modulate internal DPWM duty cycle from 0% to 100%, providing true analog-dimming behavior without external PWM generation. This mode uses the BOSC capacitor to set dimming frequency (1.2–2 kHz) and avoids microcontroller dependency.

How does open-string protection work without dedicated sensing per string?

Open-string detection relies on monitoring LEDX pin voltages: an open string pulls its LEDX pin near GND (<180mV), triggering automatic mark-off. The IC then regulates output voltage based only on remaining active strings, maintaining backlight functionality while flagging faults via VFAULT pin state changes.

Can MP3399EY-LF-Z drive LEDs with forward voltage exceeding 30V per string?

Yes - the boost converter output is limited only by external components (MOSFET V_DS, diode rating, capacitor voltage). With appropriate 60V+ rated external FET and diode, the IC supports >40V total string V_f; OVP threshold must be scaled accordingly using the R1/R2 divider on the OVP pin.

What is the minimum recommended ISET resistor value?

The minimum R_SET is determined by max current (60mA): R_SET(MIN) = 1.22V / 60mA = 20.3kΩ. Using lower values risks exceeding internal current sink capability and degrading matching accuracy; 22kΩ is the practical minimum per design guidelines.

Is thermal derating required for SOIC-28 at full load?

Yes - at 60mA/string (720mA total LED current) and 28V input, power dissipation exceeds 1.2W. With θ_JA = 60°C/W, junction rise exceeds 72°C above ambient; derating to ≤45mA/string or adding copper pour/thermal vias is recommended for continuous operation above 60°C ambient.

Does the ISENSE pin require connection in cascaded configurations?

In master-slave cascading, only the master IC connects ISENSE to the shared inductor sense resistor; slave ICs must tie ISENSE to GND (not float). This prevents conflicting current sensing and ensures accurate peak-current-mode control across the entire system.