Monolithic Power Systems Inc. MP2357DJ-LF-Z

Overview

MP2357DJ-LF-Z from Monolithic Power Systems is a monolithic current-mode step-down DC/DC converter with integrated 0.35Ω high-side MOSFET, delivering up to 0.5A peak output current across 4.5V–24V input range, fixed 1.4MHz switching frequency, and adjustable 0.81V–15V output voltage. It targets space-constrained industrial power rails and battery-powered pre-regulators.

For engineers reviewing the MP2357DJ-LF-Z datasheet, MP2357DJ-LF-Z pinout, MP2357DJ-LF-Z application, or MP2357DJ-LF-Z equivalent, key selection criteria include thermal shutdown behavior at 150°C, cycle-by-cycle overcurrent protection threshold of 0.8A, bootstrap capacitor requirements for BST pin, and compatibility with low-ESR ceramic output capacitors.

Technical Context

The MP2357DJ-LF-Z implements peak current-mode control with internal slope compensation, enabling stable operation with minimal external components and fast transient response. Its error amplifier compares FB voltage against a 0.81V bandgap reference and integrates the difference to adjust peak inductor current.

Operation relies on a 1.4MHz oscillator driving an RS flip-flop that controls the internal MOSFET switch; feedback loop stability is ensured by internal compensation, eliminating need for external Type-II/III networks. The BST pin requires a 0.1–1µF capacitor between SW and BST to sustain gate drive above VIN during high-duty-cycle operation.

Key Specifications

Pinout & Package

MP2357DJ-LF-Z is housed in a TSOT23-6 package (0.95mm pitch, 2.9mm × 1.6mm footprint), featuring exposed pad for thermal enhancement. Pin 1 is bottom-left when viewing top marking left-to-right.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP2331H and TPS62825RVL, MP2357DJ-LF-Z offers unique 24V input support and fixed 1.4MHz timing in TSOT23-6, making it suitable for cost-optimized industrial pre-regulators where higher current or ultra-low input voltage are unnecessary.

Availability

MP2357DJ-LF-Z is available at Aetrix Electronics and suitable for distributed power systems, battery chargers, and pre-regulators for linear regulators requiring stable component supply and long-term industrial availability.

Supply support for MP2357DJ-LF-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 mixed-signal ICs for power management, motion control, and automotive applications.

The MP2357 belongs to MPS's high-voltage buck converter product line, designed specifically for industrial and automotive subsystems needing robust 24V-input DC/DC conversion in ultra-small packages.

FAQ

What is the maximum recommended output current for MP2357DJ-LF-Z?

The MP2357DJ-LF-Z delivers up to 0.5A peak output current under thermal limits. However, the datasheet specifies that maximum load current must be reduced if duty cycle exceeds 35%, due to internal power dissipation constraints in the TSOT23-6 package. At 12V input → 3.3V output (27.5% duty), full 0.5A is supported; at 5V input → 3.3V (66% duty), output current should be limited to ~0.35A to maintain safe junction temperature.

Can MP2357DJ-LF-Z operate without an external Schottky diode?

No - MP2357DJ-LF-Z requires an external Schottky diode (e.g., SS14 or equivalent) connected from SW to output ground. Unlike synchronous buck converters, it uses an internal high-side MOSFET paired with an external freewheeling diode. Omitting the diode causes catastrophic failure during switch-off due to inductor flyback voltage exceeding absolute maximum ratings.

Is the BST capacitor mandatory, and what value is recommended?

Yes - the BST capacitor (0.1µF to 1µF, X7R ceramic) between SW and BST pins is mandatory to sustain gate drive voltage above VIN for the internal MOSFET. Without it, the high-side switch cannot turn on fully, causing excessive R_DS(ON) heating and regulation failure. The datasheet recommends 0.1µF minimum; 0.22µF is typical for 12V–24V inputs.

Does MP2357DJ-LF-Z support output voltages below 0.81V?

No - the internal bandgap reference is fixed at 0.81V, and the FB pin is designed to regulate precisely to this voltage via external resistor divider. Attempting to set output below 0.81V violates the feedback architecture and results in unregulated, unstable output. For sub-0.8V rails, a different converter with adjustable reference or external error amplifier is required.

What is the purpose of the frequency foldback feature?

Frequency foldback lowers the switching frequency from 1.4MHz to ~460kHz when FB voltage drops below 250mV - typically during output short-circuit or severe overload. This reduces average switch current and thermal stress, allowing the device to survive fault conditions longer than constant-frequency operation would permit, while maintaining cycle-by-cycle current limiting.

How does the EN pin behave during power-up?

The EN pin has a 2.8V typical UVLO threshold with 150mV hysteresis. When input voltage rises, the device remains disabled until VIN exceeds ~2.8V and EN is pulled above 1.2V. If EN is tied directly to VIN, startup occurs after VIN stabilizes above 2.8V; adding an RC delay on EN enables controlled sequencing relative to other rails.

Is MP2357DJ-LF-Z RoHS compliant and halogen-free?

Yes - the "-LF" suffix in MP2357DJ-LF-Z denotes lead-free, RoHS-compliant packaging per JEDEC J-STD-020. The device meets IPC/JEDEC J-STD-070B for halogen content (<900ppm Cl, <900ppm Br, <1500ppm total halogens), confirmed in MPS's official compliance documentation for this part number.