Monolithic Power Systems Inc. MP1540DJ-LF-P

Overview

MP1540DJ-LF-P from Monolithic Power Systems is a 5-pin TSOT23-5 current-mode step-up DC/DC converter with 1.3MHz fixed switching frequency, 18V maximum output voltage, 2.5V–6V input range, and integrated 0.65Ω MOSFET switch. It delivers up to 200mA at 12V from a 5V supply and features internal soft-start, UVLO (2.45V threshold), thermal shutdown (160°C), and current limiting (1.9A typical) for battery-powered flash and display bias applications.

For engineers reviewing the MP1540DJ-LF-P datasheet, MP1540DJ-LF-P pinout, MP1540DJ-LF-P application, or MP1540DJ-LF-P equivalent, key selection criteria include its 1.3MHz operation enabling sub-2mm-height magnetics, 1.25V feedback reference accuracy (±4%), EN pin control logic (1.3V turn-on threshold), and TSOT23-5 thermal resistance (θJA = 220°C/W).

Technical Context

The MP1540DJ-LF-P implements a fixed-frequency peak-current-mode boost architecture with internal ramp compensation to suppress subharmonic oscillation above 50% duty cycle. Its error amplifier compares FB voltage against a 1.25V bandgap reference and drives PWM comparator via stabilized current-sense signal.

Control loop stability relies on internal compensation (20kHz zero) plus external FB network-requiring series resistor (47kΩ–100kΩ) between divider and FB pin-and accounts for right-half-plane zero (fRHPZ) induced by continuous-conduction-mode operation, mandating crossover frequency ≤75kHz and ≥1 decade below fRHPZ.

Key Specifications

Pinout & Package

MP1540DJ-LF-P is housed in a 5-pin TSOT23-5 package (2.9mm × 1.6mm × 0.87mm, 0.95mm lead length), optimized for low thermal resistance (θJA = 220°C/W) and high-density PCB layout.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar step-up converter applications.

Compared with TPS61040DRVR and MAX1706ESA+, MP1540DJ-LF-P offers superior integration (EN pin, soft-start, tighter FB tolerance), smaller solution size due to 1.3MHz operation, and better thermal protection granularity-making it optimal for space-constrained, battery-sensitive flash and display applications.

Availability

MP1540DJ-LF-P is available at Aetrix Electronics and suitable for camera phone flash circuits, small LCD display bias supplies, digital still camera sensor rails, and USB-powered external modem interfaces requiring stable component supply across production volumes and extended lifecycle planning.

Supply support for MP1540DJ-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 design centers in the US, China, and Taiwan, and global distribution through authorized partners.

The MP1540 belongs to MPS's low-power DC/DC boost converter product line, engineered specifically for portable consumer electronics requiring compact, efficient, and robust voltage step-up solutions from single-cell batteries.

FAQ

What is the recommended input capacitor value and placement for MP1540DJ-LF-P?

A minimum 4.7µF X5R/X7R ceramic capacitor with low ESR is required, placed physically adjacent to the IN pin and GND pin. This placement minimizes high-frequency ripple current loop area, reduces input voltage noise, and prevents EMI coupling into adjacent analog circuitry such as image sensors or audio amplifiers.

Can MP1540DJ-LF-P operate with a 3.3V input to generate 12V output?

Yes - MP1540DJ-LF-P supports input voltages from 2.5V to 6V and can deliver 12V at up to 200mA from a 3.3V source. Efficiency drops to ~78% at 3.3V→12V/200mA (per typical curves), requiring attention to thermal layout and output capacitance to maintain regulation under load transients.

What diode is recommended for the MP1540DJ-LF-P boost circuit?

The MBR0520 Schottky diode is recommended for loads ≤500mA due to its 20V reverse rating, low forward voltage (~0.35V), and fast recovery. For higher average currents or improved thermal margin, the Microsemi UPS5817 (20V, 1A) is specified as an alternative with lower VF and higher surge capability.

How does the EN pin behave when left unconnected?

The EN pin must never be left floating. If unused, it must be tied directly to the IN supply rail to ensure automatic startup. An internal pull-down keeps the device disabled when EN is at 0V; the rising threshold is 1.3V typical with 100mV hysteresis to prevent chatter near the trip point.

What is the purpose of the 100pF capacitor shown in the typical application schematic (Figure 2)?

The 100pF capacitor (C3) from FB to GND provides high-frequency noise filtering on the feedback node, improving immunity to switching noise coupling. It forms a low-pass filter with the FB divider resistors, reducing susceptibility to radiated EMI without affecting DC regulation accuracy or loop stability.

Does MP1540DJ-LF-P support adjustable output voltage?

Yes - output voltage is fully adjustable using an external resistor divider connected to the FB pin. With a fixed 11.8kΩ lower resistor (R2), the upper resistor (R1) is calculated as R1 = 9.44kΩ × (VOUT − 1.25V). This allows precise setting from 3V to 18V while maintaining 1.25V reference accuracy.

What is the maximum duty cycle limitation and how does it affect design?

The MP1540DJ-LF-P has a maximum duty cycle of 85%, limiting achievable output voltage based on input. At VIN = 2.5V, VOUT(max) ≈ 16.7V (2.5V / (1 − 0.85)); at VIN = 5V, VOUT(max) ≈ 33.3V - though absolute max rated output is 18V per Absolute Maximum Ratings. Designers must ensure selected VOUT stays within both electrical and thermal limits.