Monolithic Power Systems Inc. MP28258DD-A-LF-Z

Overview

MP28258DD-A-LF-Z from Monolithic Power Systems is a fully integrated, synchronous step-down DC/DC converter delivering 3A continuous output current with 4.2V–20V input range, 0.815V–13V adjustable output, and proprietary Constant-On-Time (COT) control for fast transient response in networking and distributed power systems.

For engineers reviewing the MP28258DD-A-LF-Z datasheet, MP28258DD-A-LF-Z pinout, MP28258DD-A-LF-Z application, or MP28258DD-A-LF-Z equivalent, key selection criteria include hiccup-mode OCP behavior, QFN12 (2×3mm) thermal performance (θJA = 70°C/W), PG open-drain timing (0.5ms delay), and bootstrap-driven high-side gate drive requiring external BST capacitor.

Technical Context

The MP28258DD-A-LF-Z implements COT control with feed-forward input voltage dependence, enabling stable switching frequency across 4.2V–20V input while maintaining VOUT/VIN duty ratio. Its internal power stage integrates 120mΩ high-side and 50mΩ low-side MOSFETs, eliminating external switches.

It features hiccup-mode over-current protection (OCP) triggered when FB drops below 50% of VREF (≈0.4V), causing automatic soft-start retry cycles until fault clearance. The power-good (PG) pin provides open-drain status with 90% rising / 85% falling thresholds and 0.5ms delay, synchronized to feedback regulation stability.

Key Specifications

Pinout & Package

MP28258DD-A-LF-Z is housed in a thermally enhanced QFN12 package (2mm × 3mm, 0.5mm pitch) with exposed thermal pad (Pin 2, 10, and exposed pad all connected to SW). The package supports ≤1.8W continuous power dissipation at 25°C ambient (θJA = 70°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP2330H, MP28258DD-A-LF-Z trades higher input voltage limit and lower quiescent current for proven hiccup-mode robustness and simpler frequency programming; versus TPS54332, it delivers faster transient response without compensation networks but lacks automotive qualification and current-mode flexibility.

Availability

MP28258DD-A-LF-Z is available at Aetrix Electronics and suitable for telecom infrastructure, industrial automation, and embedded server management applications requiring stable component supply, RoHS-compliant packaging, and long-term production continuity.

Supply support for MP28258DD-A-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 power ICs, with core expertise in DC/DC conversion, LED drivers, and motor control solutions.

The MP28258 belongs to MPS's high-efficiency synchronous buck converter product line, designed specifically for space-constrained, fast-transient industrial and networking applications where thermal performance and fault resilience are critical.

FAQ

What is the recommended minimum BST capacitor value and dielectric type?

A 0.1µF X5R or X7R ceramic capacitor is required between BST and SW pins. This value ensures sufficient charge storage for high-side gate drive across the full 4.2V–20V input range and 3A load. Use NP0/C0G only if temperature stability is critical; X5R/X7R offer better volumetric efficiency and are validated in MPS reference designs.

Does MP28258DD-A-LF-Z support forced PWM mode, or is skip mode automatic?

The MP28258DD-A-LF-Z operates exclusively in automatic mode: it uses CCM at heavy loads and transitions seamlessly to skip mode at light loads to maximize efficiency. There is no pin or register to force continuous PWM; this behavior is inherent to its COT architecture and current-modulator design.

How does the hiccup-mode OCP behave during a sustained short circuit?

Under sustained short, the device disables output, discharges the internal soft-start capacitor, waits ~10–100ms, then attempts soft-start again. Each retry cycle repeats until VFB rises above 50% VREF. This prevents thermal damage while allowing automatic recovery when the fault clears-no manual reset or power cycle is needed.

Can the FREQ pin be left unconnected or tied directly to GND?

No. The FREQ pin must be connected to VIN through a resistor (R7) to set switching frequency; leaving it floating or grounding it disables frequency control and may cause erratic operation or failure to start. A 1nF decoupling capacitor to GND is mandatory per datasheet layout guidelines.

Is the exposed thermal pad electrically connected, and how should it be soldered?

Yes-the exposed pad is internally connected to SW (switch node), not GND. It must be soldered to a dedicated SW copper pour using ≥4 thermal vias (0.3mm diameter) to an inner ground or power plane. Do not connect it to GND; incorrect pad connection causes shoot-through and immediate failure.

What is the maximum allowable output capacitance for stable operation?

No hard upper limit exists, but total output capacitance >1000µF may increase soft-start time and reduce transient response speed. For ceramic outputs, keep ESR <10mΩ and use external ramp compensation (R4/C4) if COUT > 470µF. Electrolytic/POSCAP caps require larger ESR (≥5mΩ) to ensure inherent slope compensation.

Does MP28258DD-A-LF-Z support output voltages below 0.815V?

No. The internal reference is trimmed to 815mV ±12mV, and the datasheet specifies 0.815V as the absolute minimum output. Attempting lower outputs via external resistors violates regulation accuracy and may cause instability or PG deassertion due to FB undershoot.