Monolithic Power Systems Inc. MP3385GR-Z

Overview

MP3385GR-Z from Monolithic Power Systems is a 4-string, 80V-rated WLED controller with I²C interface, designed for LCD panel backlighting in desktop monitors and all-in-one systems. It delivers up to 300mA per string with 1.8% current matching, supports 4.5–33V input, and regulates output via external MOSFET using peak-current-mode PWM control.

For engineers reviewing the MP3385GR-Z datasheet, MP3385GR-Z pinout, MP3385GR-Z application, or MP3385GR-Z equivalent, key selection criteria include programmable 100–900kHz switching frequency, 10-bit internal dimming resolution, 80V absolute string rating, auto-detection of unused LED strings at startup, and cascading capability with single power source.

Technical Context

The MP3385GR-Z implements a peak-current-mode step-up converter with an internal 6V LDO (VCC) powering gate driver and control circuitry. Its regulation loop uses COMP-based error amplification and dynamically selects the lowest active LEDX voltage to set bus voltage, ensuring tight output regulation across variable string configurations.

I²C-controlled operation enables real-time configuration of dimming mode (PWM/analog/mixed), OVP threshold (18–74V, 2V/step), OCP threshold (0.15–0.5V, 50mV/step), and switching frequency - all without external component changes. Fault detection includes open/short-string identification, thermal shutdown (150°C latch-off), and cycle-by-cycle current limiting.

Key Specifications

Pinout & Package

MP3385GR-Z is housed in a thermally enhanced QFN-20 package (4mm × 4mm, exposed pad), optimized for high-power LED driver applications requiring low θ_JA (42°C/W) and efficient heat dissipation to PCB ground plane.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MPQ3385GR-A, MP3385GR-Z trades automotive qualification for lower cost and identical feature set in commercial environments; versus LM3409QMH/NOPB, it adds digital control, precision dimming, and intelligent fault handling - justifying its use in adaptive, software-defined backlight systems.

Availability

MP3385GR-Z is available at Aetrix Electronics and suitable for desktop LCD flat panel displays, all-in-one PCs, and industrial HMI displays requiring stable component supply, long-term lifecycle support, and traceable sourcing for production programs.

Supply support for MP3385GR-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 power ICs, with design centers in the US, China, and Taiwan, and global manufacturing partnerships.

The MP3385 product line targets medium-to-large LCD backlighting applications, emphasizing digital configurability, multi-string precision, and robust fault management - addressing the shift from fixed-function to software-defined display power systems.

FAQ

What is the maximum LED string voltage the MP3385GR-Z can regulate?

The MP3385GR-Z supports an absolute maximum rating of 80V per LED string, with programmable over-voltage protection (OVP) thresholds ranging from 18V to 74V in 2V steps. This allows safe operation with up to ~22 white LEDs in series (assuming 3.2V typical Vf) while retaining 10V margin for Vf variation and temperature drift.

Does MP3385GR-Z require an external MOSFET, and what are the gate drive specifications?

Yes, MP3385GR-Z requires an external N-channel MOSFET for the boost converter. Its DRV pin provides 4Ω source and 2Ω sink impedance at 6V VCC, supporting gate charge delivery for MOSFETs with Qg ≤ 25nC. A 10Ω series gate resistor is recommended to damp ringing and limit peak current.

How does the unused LED string auto-detection function work during startup?

At power-on, MP3385GR-Z monitors LEDX pin voltages before initiating boost switching. If any LEDX pin remains below 206mV (indicating open circuit or disconnection), that channel is automatically disabled in register 00H and excluded from regulation - preventing OVP triggering and enabling reliable startup with 1–3 active strings.

Can MP3385GR-Z operate in analog dimming mode without an external PWM signal?

Yes - when INTERFACE bit (register 00H, bit 2) is set to '1', analog dimming is controlled entirely via I²C registers 03H and 04H, eliminating the need for external PWM. The internal 23kHz carrier ensures flicker-free operation, and 10-bit resolution enables precise 0–100% intensity control without MCU GPIO involvement.

What thermal protection behavior does MP3385GR-Z exhibit under sustained overload?

MP3385GR-Z features recoverable thermal shutdown: it latches off at 150°C junction temperature and resumes operation only after die temperature falls to 125°C (25°C hysteresis). This avoids permanent blackouts in thermally constrained enclosures while providing clear fault indication via the FT pin and OTP_F bit in register 03H.

Is the QFN-20 package of MP3385GR-Z compatible with standard reflow profiles?

Yes - MP3385GR-Z's QFN-20 (4mm × 4mm) package is rated for lead-free reflow with peak temperature up to 260°C (per JEDEC J-STD-020). The exposed thermal pad must be soldered to a minimum 4-layer PCB with ≥4 thermal vias to ensure θ_JA = 42°C/W and prevent derating above 85°C ambient.