Monolithic Power Systems Inc. MP3385GF

Overview

MP3385GF from Monolithic Power Systems is a 4-string, 80V absolute-rated WLED controller with I²C interface, peak-current-mode PWM boost architecture, and programmable 100–900 kHz switching frequency. It drives external N-MOSFETs to regulate up to 300 mA per string with 1.8% current matching, targeting LCD backlighting in desktop monitors and all-in-one PCs.

For engineers reviewing the MP3385GF datasheet, MP3385GF pinout, MP3385GF application, or MP3385GF equivalent, key selection criteria include its 4.5–33 V input range, I²C-configurable dimming modes (PWM/analog/mixed), 80 V string voltage rating, auto-detection of unused LED strings at startup, and thermal/overvoltage/short-string protection.

Technical Context

The MP3385GF implements a peak-current-mode, constant-frequency boost converter with an internal 6 V LDO (VCC) powering gate drivers and control circuitry. Its regulation loop uses COMP-based error amplification and dynamically selects the lowest active LEDX voltage to set output bus voltage.

Dimming is fully configurable via I²C: six modes (direct PWM, internal 23 kHz PWM, analog via pulse, internal analog, and two mixed modes with 25% or 50% transfer points) support 10-bit internal dimming resolution and 8-bit full-scale current programming (2–100%).

Key Specifications

Pinout & Package

TSSOP20-EP package (4.4 mm × 6.5 mm, 0.65 mm pitch) with exposed thermal pad connected to GND for enhanced thermal dissipation in high-current backlight applications.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP3384GF and RT8581GSP, the MP3385GF uniquely combines 4-string support, 80 V string rating, I²C programmability, and auto-detection-making it optimal for scalable, high-reliability LCD backlight systems demanding field-upgradable dimming profiles and robust fault handling.

Availability

MP3385GF is available at Aetrix Electronics and suitable for desktop LCD flat panel displays, all-in-one PCs, and industrial HMI display panels requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MP3385GF 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 MP3385 product line targets LCD backlighting applications, delivering integrated, digitally configurable WLED controllers that replace discrete boost + current sink solutions while enhancing reliability and design flexibility.

FAQ

What is the maximum LED string voltage the MP3385GF can safely regulate?

The MP3385GF has an absolute maximum rating of 80 V per LED string, with programmable overvoltage protection (OVP) thresholds ranging from 18 V to 74 V in 2 V steps. This allows safe operation with up to 14 white LEDs in series under worst-case forward-voltage conditions (e.g., cold temperature, high current), while protecting against open-string faults.

How does the MP3385GF achieve 1.8% current matching between strings?

The MP3385GF achieves 1.8% current matching through matched internal current-sink transistor design, precision ISET reference voltage (1.98 V ±25 mV), and layout-optimized routing of LED1–LED4 outputs. Matching is measured at 200 mA per string and remains stable across temperature (–40°C to +125°C) and supply voltage variations, eliminating need for external trimming.

Can the MP3385GF operate without an external microcontroller?

Yes-the MP3385GF supports standalone operation using the PWM pin for analog or direct PWM dimming without I²C. Default settings (e.g., 400 kHz switching, 23 kHz internal PWM, 201 mA full-scale current) are active at power-up. I²C is optional for advanced configuration like mixed dimming, OVP threshold tuning, or unused-string disablement.

What thermal performance can be expected in TSSOP20-EP package at full load?

In TSSOP20-EP with proper PCB copper pour (≥2 cm² thermal pad area), the MP3385GF achieves θ_JA = 40°C/W. At 300 mA/string × 4 strings and 12 V input, typical power dissipation is ~1.2 W, resulting in ~48°C junction rise above ambient-well below the 150°C shutdown threshold and enabling continuous operation at +85°C ambient.

Does the MP3385GF support daisy-chaining for multi-controller synchronization?

No-the MP3385GF does not support daisy-chained I²C or clock synchronization. However, it supports cascading: one device acts as master (IS pin connected to sense resistor), others as slaves (IS tied to GND), sharing the same VIN and enabling coordinated boost operation from a single input source without timing skew.

What happens if the I²C interface is left unconnected during operation?

If I²C lines (SCL/SDA) are floating or unconnected, the MP3385GF operates using factory-default register values: 400 kHz switching, PWM dimming mode (MODE=00), INTERFACE=0, full-scale current = 201 mA, OVP = 36 V, and OCP = 300 mV. All protection features remain active, and the device functions fully-only advanced configuration requires I²C.

Is the LPF pin required for all dimming modes?

No-the LPF pin is only used in analog and mixed dimming modes when external PWM input is applied. A capacitor (typically 100 nF) between LPF and GND filters the PWM signal into a DC control voltage. In direct PWM dimming mode, the LPF capacitor must be omitted to avoid interference with the raw PWM signal path.