Monolithic Power Systems Inc. MP28251GD-P

Overview

MP28251GD-P from Monolithic Power Systems is a synchronous step-down DC/DC converter with integrated 60mΩ high-side and 30mΩ low-side MOSFETs, delivering up to 4A continuous output current across a 4.75V–20V input range. It features programmable switching frequency (400–600kHz typical), internal 0.815V feedback reference, and thermal shutdown at 150°C - deployed in DSL/cable modems for compact, high-efficiency 3.3V/4A local power rails.

For engineers reviewing the MP28251GD-P datasheet, MP28251GD-P pinout, MP28251GD-P application, or MP28251GD-P equivalent, key selection criteria include its QFN-14 (2×3mm) package thermal resistance (θJA = 70°C/W), EN-controlled startup delay via external capacitor, LPM-selectable light-load operation mode, and FREQ/SYNC pin compatibility with external 300kHz–2MHz clocks.

Technical Context

The MP28251GD-P employs fixed-frequency peak-current-mode control with an internal 5V bias regulator powered from VIN, enabling full-range operation down to 4.75V input. Its error amplifier compares FB voltage against a trimmed 0.815V reference and drives COMP to regulate inductor current via the high-side switch.

Current limiting triggers hiccup-mode protection when inductor peak current exceeds 5.6A and output drops below 70% of setpoint; thermal shutdown activates at 150°C with 30°C hysteresis. Bootstrap charging uses an internal floating driver with UVLO (2.2V rising threshold) and optional external diode support for high-duty-cycle applications.

Key Specifications

Pinout & Package

MP28251GD-P is housed in a thermally enhanced 14-pin QFN package measuring 2mm × 3mm with exposed thermal pad. The package supports high-power density layouts via multiple GND pins (1,12,13,14) and wide-copper-area routing for IN, SW, and GND paths.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP28251GD-P, MP2384GQ-P offers lower R_DS(on) and wider input range but requires updated layout for its 3×3mm QFN-16 package; RT7295BGJ6F provides pin-compatible drop-in replacement in some cases but sacrifices LPM flexibility and sync functionality.

Availability

MP28251GD-P is available at Aetrix Electronics and suitable for DSL modems, cable modems, and set-top boxes requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for MP28251GD-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 mixed-signal ICs for power management, motion control, and automotive applications.

The MP28251 belongs to MPS's high-efficiency synchronous buck converter product line, engineered for space-constrained broadband and consumer electronics where thermal performance, small footprint, and robust protection are critical.

FAQ

What is the maximum recommended output current for MP28251GD-P under continuous operation?

The MP28251GD-P is rated for 4A continuous output current at TA = +25°C with proper PCB thermal design (2-layer board, 1-in² 2oz copper on top/bottom layers). Derating is required above 60°C ambient; at 85°C, max continuous output drops to ~2.8A based on θJA = 70°C/W and TJ(max) = 125°C.

Can MP28251GD-P operate with an input voltage below 4.75V?

No - the absolute minimum operating input voltage is 4.75V per datasheet specifications. Input voltage below this threshold triggers UVLO, disabling the regulator. The UVLO rising threshold is 4.25V, but reliable operation requires ≥4.75V to ensure stable VCC regulation and gate drive strength.

How does the LPM pin affect efficiency and output ripple?

When LPM is pulled high, the device enters pulse-skipping mode (PSM) under light load (<100mA), improving efficiency by reducing switching losses. However, PSM increases output voltage ripple due to variable-frequency operation. Grounding LPM forces continuous conduction mode (CCM), lowering ripple but reducing light-load efficiency by ~5–8%.

Is an external bootstrap diode required for MP28251GD-P?

An external bootstrap diode (e.g., IN4148) is optional and recommended only when duty cycle exceeds 65% (e.g., VOUT ≥ 5V with VIN = 12V). It improves bootstrap capacitor charging efficiency and reduces BST voltage droop, especially in high-duty-cycle applications like 5V-out converters.

What is the purpose of the FREQ/SYNC pin's dual functionality?

The FREQ/SYNC pin serves two roles: (1) with a resistor to GND, it sets internal oscillator frequency (400–600kHz); (2) when driven by an external CMOS clock (300kHz–2MHz), it synchronizes switching edges to that clock. This enables EMI reduction and multi-rail phase alignment in complex power systems.

Does MP28251GD-P support pre-biased output startup?

Yes - the MP28251GD-P detects pre-biased outputs during startup. If the FB voltage exceeds the soft-start capacitor voltage at power-on, the controller disables both HS and LS switches until the SS capacitor charges past the FB voltage, preventing reverse current flow into the output rail.

What is the thermal pad connection requirement for the QFN-14 package?

The exposed thermal pad (EPAD) must be soldered to a solid GND plane using ≥4 thermal vias (0.3mm diameter) filled with solder or conductive epoxy. The EPAD is internally connected to GND pins (1,12,13,14); omitting this connection degrades θJA by >25°C/W and risks thermal shutdown under 4A load.