Monolithic Power Systems Inc. MP2355DN-LF-Z

Overview

MP2355DN-LF-Z from Monolithic Power Systems is a 3A, 380kHz synchronous step-down DC/DC converter with integrated 100mΩ high-side MOSFET and 10Ω low-side switch, operating from 4.75V to 23V input and delivering regulated output down to 1.222V; it features cycle-by-cycle over-current protection, thermal shutdown, and programmable soft-start via external capacitor - used in battery chargers and pre-regulators for linear regulators.

For engineers reviewing the MP2355DN-LF-Z datasheet, MP2355DN-LF-Z pinout, MP2355DN-LF-Z application, or MP2355DN-LF-Z equivalent, this page delivers verified electrical parameters (e.g., 1.222V feedback threshold, 95% peak efficiency), SOIC8N exposed-pad package details, functional pin roles, real-world load transient behavior, and validated alternative parts for design continuity.

Technical Context

The MP2355DN-LF-Z implements current-mode control with internal transconductance error amplifier (G_EA = 800μA/V) and slope-compensated PWM, enabling fast load transient response and stable loop compensation across ceramic or electrolytic output capacitors. Its fixed 380kHz oscillator sets switching frequency with ±13% tolerance (330–430kHz).

It integrates dual N-channel MOSFETs - high-side R_DS(ON) = 95mΩ, low-side R_DS(ON) = 10Ω - and uses bootstrap capacitor (BST–LX) to drive the high-side gate above VIN. UVLO triggers at 2.54V (rising) with 210mV hysteresis, and RUN pin enables operation above 2.71V.

Key Specifications

Pinout & Package

MP2355DN-LF-Z is housed in an SOIC-8 narrow-body package with exposed thermal pad on the underside, requiring solder connection to Pin 5 (GND) for optimal thermal performance (θ_JA = 50°C/W, θ_JC = 10°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP2355DN-LF-Z, MP2357DN-LF-Z offers higher current headroom at the cost of reduced light-load efficiency, while TPS54331DR trades integration for flexibility in compensation and frequency tuning - making MP2355DN-LF-Z optimal for cost-sensitive, space-constrained 3A applications needing minimal external components.

Availability

MP2355DN-LF-Z is available at Aetrix Electronics and suitable for battery chargers, distributed power systems, and embedded core voltage supplies requiring stable component supply, RoHS-compliant packaging, and full production traceability.

Supply support for MP2355DN-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 MP2355 belongs to MPS's high-efficiency integrated buck converter product line, designed specifically for compact, thermally constrained DC/DC applications where minimal external components and robust protection are mandatory.

FAQ

What is the minimum recommended output capacitance for stable operation?

The MP2355DN-LF-Z is stable with ≥22μF ceramic output capacitance (X5R/X7R) and ESR <10mΩ. Lower values may cause instability or excessive ripple; for aluminum electrolytic alternatives, use ≥470μF with ≤30mΩ ESR and add C6 compensation capacitor per datasheet Table 3.

Can the MP2355DN-LF-Z operate with a 5V-only input?

Yes - its 4.75V minimum input allows reliable operation from standard 5V rails. For best efficiency, add an external bootstrap diode (e.g., BAT54) between VIN and BST, as recommended in Figure 3 of the datasheet for fixed 5V inputs.

How does the RUN pin interface with microcontroller GPIO?

The RUN pin accepts logic-level enable signals: drive >2.71V (min) to enable, <0.9V (max) to enter 20μA shutdown. Internal 1.8μA pull-up means a single-series 10kΩ resistor to MCU GPIO suffices for active-high control without external pull-up.

Is the exposed thermal pad electrically isolated?

No - the exposed pad on the SOIC8N package is internally connected to Pin 5 (GND). It must be soldered directly to the PCB's GND plane for both thermal dissipation (reducing θ_JA by ~20°C/W) and electrical reference integrity.

What causes the MP2355DN-LF-Z to enter current-limit foldback?

Foldback activates during sustained overload or short-circuit events when the internal current comparator detects >4.3A peak switch current. The device then reduces switching frequency to ~20–50kHz and limits average output current to protect MOSFETs and inductor.

Does the MP2355DN-LF-Z support output voltages below 1.222V?

No - the internal feedback reference is fixed at 1.222V. Output voltage is set by V_OUT = 1.222V × (1 + R1/R2); therefore, the lowest achievable regulated output is 1.222V (when R1 = 0Ω, R2 = ∞Ω), and practical minimum is ~1.25V due to resistor tolerance and noise.

How does soft-start interact with the RUN pin during power sequencing?

Soft-start initiates only after RUN rises above 2.71V. If RUN is toggled during soft-start, the SS capacitor discharges through internal clamp and restarts ramp; simultaneous assertion of RUN and SS capacitor charge ensures monotonic V_OUT rise without undershoot or oscillation.