Monolithic Power Systems Inc. MP9403EN-LF

Overview

MP9403EN-LF from Monolithic Power Systems is a monolithic synchronous step-down DC/DC converter integrating 150mΩ high-side and 100mΩ low-side MOSFETs, delivering 3A continuous output current across 4.3V–7V input range with fixed 250kHz switching frequency and adjustable 0.80V–5.50V output voltage. It enables compact power conversion in notebook computers and distributed power systems.

For engineers reviewing the MP9403EN-LF datasheet, MP9403EN-LF pinout, MP9403EN-LF application, or MP9403EN-LF equivalent, key selection criteria include its integrated FETs, 1μA shutdown current, cycle-by-cycle overcurrent protection, thermal shutdown at 160°C, and compatibility with low-ESR ceramic output capacitors.

Technical Context

The MP9403EN-LF employs current-mode control architecture with internal transconductance error amplifier (820μA/V), 250kHz oscillator, and dedicated COMP pin for loop compensation. Its block diagram confirms dual N-channel MOSFET integration, bootstrap-driven high-side gate, and 0.80V precision feedback reference.

It features programmable soft-start via external SS capacitor, input UVLO with 3.65V threshold and 45mV hysteresis, and overvoltage protection triggered at 0.95V on FB. The device operates from –20°C to +125°C junction temperature and uses an exposed-pad SOIC8E package for thermal enhancement.

Key Specifications

Pinout & Package

MP9403EN-LF is housed in a thermally enhanced 8-pin SOIC package with exposed pad (SOIC8E), requiring solder connection of the exposed pad to a dedicated ground plane for optimal thermal performance and electrical stability.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous buck regulator applications.

Compared with MP2307DN-LF-Z and TPS54302DDAR, MP9403EN-LF delivers optimal balance of input voltage fit (4.3V–7V), thermal performance (exposed pad), and minimal external components-making it superior for space-constrained, battery-adjacent, or thermally limited 3A buck applications.

Availability

MP9403EN-LF is available at Aetrix Electronics and suitable for notebook computers, distributed power systems, industrial HMIs, and embedded vision modules requiring stable component supply, long-lifecycle availability, and RoHS-compliant packaging.

Supply support for MP9403EN-LF 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 MP9403 belongs to MPS's integrated synchronous buck regulator product line, designed specifically for compact, high-efficiency mid-current power conversion in portable and space-constrained embedded systems.

FAQ

What is the minimum recommended output capacitance for stable operation?

The MP9403EN-LF is stable with low-ESR ceramic capacitors; typical designs use two 22μF X5R/X7R ceramics in parallel (total 44μF). Minimum effective capacitance depends on output voltage and load step, but 22μF is validated across 1.2V–3.3V outputs with <1% output deviation under 3A transient steps.

Can the MP9403EN-LF operate with an input voltage below 4.3V?

No. The absolute minimum input voltage is 4.3V per datasheet specifications, enforced by internal UVLO that holds the regulator disabled until VIN rises above 3.65V. Operation below 4.3V risks failure to regulate or undefined behavior, and is outside guaranteed operating conditions.

Is an external Schottky diode required for basic operation?

No. The MP9403EN-LF integrates both high- and low-side MOSFETs and operates fully synchronously without external diodes. The B320 diode shown in typical schematics is optional and only improves efficiency by ~0.5–1% under heavy loads when body diode conduction dominates.

How is the soft-start duration calculated from the SS capacitor value?

Soft-start time is linearly proportional to SS capacitor value: t_SS ≈ C_SS × 167ms/μF. For example, a 0.1μF capacitor yields ~16.7ms ramp time. This relationship is derived from the internal 6μA soft-start current source charging the external capacitor to 1V.

What is the maximum allowable power dissipation at 60°C ambient temperature?

Using θ_JA = 50°C/W and T_J(MAX) = 150°C, maximum continuous power dissipation is (150°C − 60°C)/50°C/W = 1.8W. Exceeding this causes thermal shutdown; actual usable power depends on PCB copper area and airflow.

Does the COMP pin require mandatory external compensation components?

Yes. The COMP pin is the error amplifier output and must be externally compensated with at minimum a series RC network (e.g., 6.8kΩ + 4.7nF for 2.5V output) to ensure stability and adequate phase margin. Leaving COMP unconnected results in oscillation or regulation failure.

What is the purpose of the exposed pad, and how must it be connected?

The exposed pad is electrically connected to internal GND and serves as the primary thermal path. It must be soldered to a dedicated PCB ground plane with ≥4 thermal vias (0.3mm diameter) connecting to inner/ground layers to achieve rated θ_JA = 50°C/W and sustain 3A continuous operation.