Monolithic Power Systems Inc. MP1531DQ-LF-P

Overview

MP1531DQ-LF-P from Monolithic Power Systems is a triple-output DC/DC converter IC for TFT LCD bias generation, integrating a 250kHz fixed-frequency step-up converter (up to 22V), a ±10mA linear regulator pair (GH up to +38V, GL down to –20V), and internal power-on sequencing-all in a 3×3mm QFN-16 package. It operates from 2.7V–5.5V input and delivers regulated VGH/VGL/VMAIN for active-matrix display panels.

For engineers reviewing the MP1531DQ-LF-P datasheet, MP1531DQ-LF-P pinout, MP1531DQ-LF-P application, or MP1531DQ-LF-P equivalent, key selection criteria include its integrated charge-pump–driven linear regulators, 1μA shutdown current, internal soft-start timing control via CT pin, and fault-sensing RDY flag with 6ms timeout-critical for reliable TFT panel power-up in portable displays.

Technical Context

The MP1531DQ-LF-P implements a current-mode controlled step-up converter with 250mΩ internal N-channel MOSFET switch and cycle-by-cycle overcurrent protection. Its feedback architecture uses separate error amplifiers for main output (FB1), positive regulator (FB3), and negative regulator (FB2), each referenced to 1.25V (FB1/FB3) or GND (FB2).

Power-on sequencing is hardware-controlled: step-up converter enables first, followed by GL (negative regulator), then GH (positive regulator), all ramped via CT capacitor timing. Fault detection monitors FB voltages; if any falls below 80% of regulation threshold for >6ms (CT = 10nF), all outputs shut down and RDY goes high-impedance.

Key Specifications

Pinout & Package

MP1531DQ-LF-P is housed in a thermally enhanced 16-pin QFN package (3mm × 3mm, 0.5mm pitch) with exposed pad soldered to IN2 (–20V node) for optimal heat dissipation and noise isolation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar TFT LCD bias generator applications.

Compared with MAX17105ETJ+ and RT9397BF, MP1531DQ-LF-P uniquely integrates triple-output generation with autonomous sequencing and charge-pump–fed linear regulators-reducing external component count and eliminating software-dependent startup coordination required by alternatives.

Availability

MP1531DQ-LF-P is available at Aetrix Electronics and suitable for automotive infotainment displays, industrial handheld terminals, and portable medical imaging devices requiring stable component supply and long-term lifecycle support.

Supply support for MP1531DQ-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, motor drivers, and LED lighting controllers.

The MP1531 product line targets TFT LCD bias generation for portable and automotive displays, emphasizing integration, sequencing reliability, and low-quiescent-power operation in compact packages.

FAQ

What is the maximum allowable voltage difference between IN3 and IN2 pins?

The absolute maximum voltage difference between IN3 and IN2 is 60V, as specified in the Absolute Maximum Ratings table. This constraint arises from internal isolation limits of the charge-pump–driven linear regulator inputs and must be respected to prevent device damage-even if individual pin ratings (IN3 to +38V, IN2 to –20V) suggest higher differential tolerance.

Can the MP1531DQ-LF-P generate VGH = +25V and VGL = –15V simultaneously from a 3.3V input?

Yes. With appropriate external charge-pump diodes and flying capacitors, the MP1531DQ-LF-P can achieve +25V on GH (using a tripler configuration from SW) and –15V on GL (using a 2x inverter). The datasheet confirms IN3 supports up to +38V and IN2 down to –20V, and both linear regulators deliver ±10mA at those extremes with specified dropout voltages.

How does the RDY pin behave during normal operation versus fault condition?

During normal operation, RDY is actively pulled low after successful power-on sequencing and remains low as long as all FB voltages stay above 80% of their thresholds. During a fault (e.g., open feedback resistor), RDY transitions to high-impedance within ~15μs and stays there until either the fault clears or the 6ms CT-based timer expires-triggering full shutdown.

Is the exposed thermal pad on the QFN package electrically connected?

No. The exposed pad has no internal electrical connection but must be soldered to the IN2 net (–20V node) per the datasheet. This provides optimal thermal conduction path while maintaining electrical isolation-critical for safe operation given IN2's negative voltage swing and the pad's role in reducing θJA from 60°C/W to effective ~35°C/W in typical layouts.

What is the minimum recommended output capacitor for the step-up converter?

A 10μF ceramic capacitor is the minimum recommended value for the step-up converter output, as stated in the Application Information section. Lower values risk instability and excessive ripple; ceramic type is mandatory due to low ESR requirements-tantalum or aluminum electrolytics are unsuitable for this high-frequency, current-mode topology.

Does the MP1531DQ-LF-P support adjustable switching frequency?

No. The MP1531DQ-LF-P uses a fixed 250kHz oscillator with ±20% tolerance (200–300kHz). Frequency adjustment is not supported-unlike some competing boost controllers, it lacks an external resistor or capacitor frequency programming option. Layout and component selection must accommodate this fixed frequency for EMI filtering and inductor sizing.

How is power-on sequencing initiated-by EN pin or input voltage rise?

Sequencing initiates on either event: a rising edge on EN (≥1.6V) or VIN crossing the 2.25V UVLO threshold while EN is high. Both paths trigger the same internal state machine-first ramping VMAIN, then GL, then GH-ensuring deterministic startup whether controlled by MCU or battery insertion.