Monolithic Power Systems Inc. MP3385GR-P

Overview

MP3385GR-P from Monolithic Power Systems is a 4-string, 80V-rated WLED controller IC for LCD panel backlighting, implementing peak-current-mode PWM boost regulation with external MOSFET drive, I²C-programmable dimming (PWM/analog/mixed), and 1.8% string current matching at up to 300mA/string. It operates from 4.5V–33V input and supports cascaded configurations in large-format displays.

For engineers reviewing the MP3385GR-P datasheet, MP3385GR-P pinout, MP3385GR-P application, or MP3385GR-P equivalent, key selection criteria include its 100–900kHz programmable switching frequency, 8-bit full-scale current programming (2%–100%), 10-bit internal dimming resolution, 18V–80V OVP range (2V/step), and unused-string auto-detection during startup-critical for reliable backlight commissioning and fault diagnostics.

Technical Context

The MP3385GR-P uses a peak-current-mode, constant-frequency boost controller architecture with an internal 6V LDO (VCC) powering gate drivers and logic. Its four open-drain LED current sinks (LED1–LED4) regulate string current via external ISET resistor, achieving 1.8% matching across strings at 200mA.

Dimming is fully configurable via I²C: six modes (direct PWM, internal 23kHz PWM, analog, internal analog, mixed with 25% or 50% transfer point), plus programmable OCP (150–500mV), OVP (18–74V), thermal shutdown (150°C), and short/open-LED protection. The IS pin enables cycle-by-cycle current limiting and cascading support.

Key Specifications

Pinout & Package

MP3385GR-P is housed in a thermally enhanced QFN-20 package (4mm × 4mm, exposed pad). The exposed pad must be soldered to PCB ground for optimal thermal performance (θ_JA = 42°C/W, θ_JC = 9°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP3385GR-P, MPQ3385-AEC1 adds automotive qualification without sacrificing features, while RT8546GSP trades configurability and channel count for lower BOM cost and simpler layout-making MP3385GR-P optimal for mid-to-high-end commercial displays needing precision and flexibility.

Availability

MP3385GR-P is available at Aetrix Electronics and suitable for desktop LCD flat panels, All-in-One PCs, and commercial digital signage requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

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

The MP3385 product line targets high-efficiency, digitally configurable LED backlighting for mid-to-large LCD panels-designed to replace discrete solutions with integrated protection, precision matching, and flexible dimming in compact QFN packages.

FAQ

What is the minimum recommended ISET resistor value for full-scale 300mA per string?

The MP3385GR-P specifies VISET = 1.98V (typical) and requires ILED = V_ISET / R_ISET. For 300mA/string, R_ISET = 1.98V / 0.3A = 6.6kΩ. However, the absolute maximum string current is 300mA, and the datasheet confirms stable operation down to R_ISET = 6.25kΩ (317mA), so 6.6kΩ is the practical minimum for rated operation.

Can MP3385GR-P drive more than 4 LED strings using external multiplexing?

No-MP3385GR-P has exactly four dedicated open-drain LED current sinks (LED1–LED4) and no provision for external current sink expansion. Cascading multiple MP3385GR-P units (via IS pin synchronization) is supported, but each IC independently drives only up to 4 strings.

Is the 23kHz internal PWM dimming frequency fixed or adjustable?

The 23kHz internal PWM frequency is fixed and not user-adjustable; it is generated by an internal oscillator and applies only in I²C-controlled PWM or mixed dimming modes (INTERFACE = 1). External PWM input frequency remains unrestricted and determines dimming ratio in direct PWM mode.

How does the unused-string auto-detection function interact with I²C configuration after power-on?

Unused-string auto-detection runs exclusively during initial power-up before I²C communication begins. If OVP threshold or other registers are modified via I²C after EN assertion, the auto-detection is disabled for that power cycle-strings must then be manually enabled/disabled via register 00H LEDx bits.

What is the maximum allowable voltage on the OVP pin during normal operation?

The OVP pin monitors boost output via a resistive divider; its absolute maximum rating is +80V. During normal regulation, the pin voltage equals (V_OUT × R2)/(R1 + R2). To avoid exceeding the 6.5V max on the pin itself, the divider must scale 80V output to ≤6.5V-typically using R1 = 1.1MΩ and R2 = 100kΩ (scaling ratio ≈ 12:1).

Does MP3385GR-P support analog dimming without an external PWM signal?

Yes-when INTERFACE = 1 in register 00H, analog dimming is controlled entirely via I²C registers 03H and 04H (DIM[9:0]), eliminating need for external PWM or LPF capacitor. This enables microcontroller-only brightness control with no additional timing signals.

What failure modes trigger the FT pin, and how are they cleared?

FT goes low on OVP, OCP, OTP, LED open/short, or diode open faults. Faults are latched until either EN is toggled low-then-high or VIN is cycled. Register 03H retains individual fault flags (OVP_F, OCP_F, etc.) until explicitly cleared via I²C write, enabling persistent fault logging.