Monolithic Power Systems Inc. MP28259DD-LF-P

Overview

MP28259DD-LF-P from Monolithic Power Systems is a fully integrated synchronous step-down DC/DC converter with Constant-On-Time (COT) control, delivering 2A continuous output current across a 4.2V–20V input range and supporting adjustable output voltages from 0.815V to 13V. It features low R_DS(ON) internal MOSFETs (130mΩ HS / 80mΩ LS), programmable switching frequency (via external resistor), and integrated power-good (PG) indicator in a compact QFN12 (2mm × 3mm) package-designed for space-constrained networking and distributed power systems.

For engineers reviewing the MP28259DD-LF-P datasheet, MP28259DD-LF-P pinout, MP28259DD-LF-P application, or MP28259DD-LF-P equivalent, key selection criteria include its COT-based fast transient response, latch-off OCP mode, thermal shutdown with 25°C hysteresis, and compatibility with both large-ESR (e.g., POSCAP) and low-ESR (ceramic) output capacitors requiring external ramp compensation.

Technical Context

The MP28259DD-LF-P employs Constant-On-Time (COT) control architecture with feed-forward input voltage dependence, enabling stable regulation and rapid load-step response without external loop compensation. Its internal high-side and low-side MOSFETs are optimized for minimal conduction loss, and dead-time control prevents shoot-through during switching transitions.

Operation includes automatic mode transition between continuous conduction mode (CCM) at heavy loads and skip-mode (light-load) operation to maintain efficiency down to light loads. Protection logic integrates cycle-by-cycle over-current detection with 50μs hold-off timing, non-latching UVLO (3.1V rising threshold), and thermal shutdown at 150°C with 25°C hysteresis.

Key Specifications

Pinout & Package

MP28259DD-LF-P is housed in a thermally enhanced, RoHS-compliant QFN12 package (2mm × 3mm, 0.5mm pitch) with an exposed thermal pad (pins 2, 10, and Exposed Pad all connected to SW). The package supports high-density PCB layouts and efficient heat dissipation via the exposed pad soldered to a thermal plane.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP28259DD-LF-P, MP28164DD-LF-Z trades PG functionality and current headroom for wider input range, while RT7272BGJ6F sacrifices COT responsiveness and frequency flexibility to achieve smaller footprint-making MP28259DD-LF-P optimal where fast transients, programmability, and system monitoring are critical.

Availability

MP28259DD-LF-P is available at Aetrix Electronics and suitable for networking equipment power rails, distributed telecom power, industrial PLC I/O modules, and embedded computing power requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MP28259DD-LF-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 MP28259 belongs to MPS's high-efficiency, fast-transient synchronous buck converter product line, engineered specifically for compact, high-reliability point-of-load regulation in networking, telecom, and industrial systems.

FAQ

What is the recommended input capacitor configuration for MP28259DD-LF-P?

A minimum 10µF X5R/X7R ceramic capacitor must be placed adjacent to the IN pin, with additional bulk capacitance (e.g., 47–100µF tantalum or POSCAP) if input ripple exceeds 50mV. RMS current rating should exceed half the maximum output current (≥1A) to handle worst-case discontinuous input current.

Does MP28259DD-LF-P support ceramic output capacitors?

Yes, but external ramp compensation (R4 and C4) is required on the FB pin to stabilize operation due to low ESR. Equation 7 defines the ramp voltage contribution, and equations 5 and 9 provide design constraints to ensure PWM-mode stability with ceramic outputs.

How does the latch-off OCP mode behave during sustained overload?

When over-current is detected for ≥50μs (OCP timer timeout), the device latches off: HS-FET and LS-FET disable, PG goes low, and the part remains off until EN is cycled low-then-high or input power is removed and reapplied.

What is the function of the exposed thermal pad on the QFN12 package?

The exposed pad (connected internally to SW) serves dual roles: it provides a low-thermal-resistance path (θ_JC = 15°C/W) to the PCB thermal plane and forms part of the high-current switch node. It must be soldered to a solid copper pour with ≥4 thermal vias to GND or SW plane.

Can MP28259DD-LF-P operate with an input voltage below 4.2V?

No-absolute minimum operating input is 4.2V per datasheet specifications. Input below this level triggers UVLO (rising threshold 3.1V), preventing startup. Attempting operation below 4.2V risks undefined behavior, failure to regulate, or intermittent shutdown.

Is the FREQ pin compatible with voltage-based frequency tuning?

No-the FREQ pin is designed exclusively for resistor-to-IN biasing per equation 3. Applying a voltage source or capacitor-only network will disrupt the internal one-shot timer and cause unpredictable switching frequency or instability.

What is the maximum allowable output voltage ripple before PG assertion is affected?

PG assertion depends on average FB voltage crossing 90% of 815mV (733.5mV). With typical 10mV p-p FB ripple, PG remains stable. However, if output ripple causes FB to dip below 85% of reference (693mV) for >0.5ms, PG may falsely deassert-so output ripple should be kept <25mV p-p at 2A load.