Monolithic Power Systems Inc. MP4558DN-LF-P

Overview

MP4558DN-LF-P from Monolithic Power Systems is a non-synchronous step-down DC/DC converter with integrated 250mΩ high-side MOSFET, 3.8V–55V input range, 1A output current, and programmable 2MHz switching frequency. It delivers up to 95% efficiency in automotive and industrial power conversion systems using ceramic output capacitors and internal soft-start.

For engineers reviewing the MP4558DN-LF-P datasheet, MP4558DN-LF-P pinout, MP4558DN-LF-P application, or MP4558DN-LF-P equivalent, key selection criteria include its 12µA shutdown current for battery operation, 0.8V feedback reference with ±2.5% tolerance, frequency fold-back during startup, thermal shutdown at 150°C, and SOIC8E package with exposed pad for thermal management.

Technical Context

The MP4558DN-LF-P employs peak-current-mode control with a transconductance error amplifier (120µA/V) and COMP pin-based loop compensation. Its internal oscillator supports resistor-programmed frequencies from 500kHz to 2MHz, with minimum on/off times of 100ns each to maintain regulation at high VIN/VOUT ratios.

It integrates bootstrap charging circuitry with 5V regulated BST supply, UVLO on EN (1.4–1.7V threshold) and VIN (2.7–3.3V rising), and cycle-by-cycle current limiting (1.3–3.5A typical). Short-circuit protection reduces current limit to ~50% when FB = 0V and folds switching frequency to limit power dissipation.

Key Specifications

Pinout & Package

MP4558DN-LF-P is housed in an SOIC8E (exposed pad) package, optimized for thermal performance in high-input-voltage step-down applications. The exposed pad must be soldered to a PCB ground plane to achieve θ_JA = 50°C/W and sustain 1A continuous output.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP4558DN-LF-P, MP4571DN-LF-Z offers higher current capability and lower conduction loss but requires revalidation of loop compensation, while LM5164QDDARQ1 adds automotive qualification and diagnostic features at the cost of higher BOM count and reduced light-load efficiency.

Availability

MP4558DN-LF-P is available at Aetrix Electronics and suitable for automotive infotainment, industrial sensor nodes, and distributed telecom power systems requiring stable component supply despite its "Not Recommended for New Designs" status.

Supply support for MP4558DN-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 power ICs, with design centers in the US, China, and Taiwan.

The MP4558 belongs to MPS's high-voltage DC/DC converter product line, engineered for robust operation in automotive, industrial, and telecom environments where wide input range and thermal resilience are critical.

FAQ

What is the maximum recommended output voltage for MP4558DN-LF-P?

The MP4558DN-LF-P supports output voltages from 0.8V to 52V, set by the external FB resistor divider. At 52V output, the device maintains regulation only if input voltage remains ≥55V minus diode drop, and thermal design accommodates reduced efficiency at high V_OUT/V_IN ratios.

Can MP4558DN-LF-P operate with a 2MHz switching frequency without external components?

Yes - a 95kΩ resistor from FREQ to GND configures 2MHz operation. However, at 2MHz, the 100ns minimum on-time limits practical duty cycle range; for VIN > 24V and VOUT < 5V, external bootstrap diode addition is recommended to ensure reliable BST capacitor charging.

Why does MP4558DN-LF-P specify "Not Recommended for New Designs"?

MPS issued this notice because MP4571 supersedes MP4558 with improved specifications: 1.2A current limit, 75mΩ R_DS(ON), lower IQ, and enhanced thermal performance. MP4558DN-LF-P remains fully functional and supported for legacy production but lacks roadmap extension.

Is the SOIC8E package thermally adequate for 1A continuous operation at 55V input?

Yes, when the exposed pad is soldered to a ≥2cm² internal or external GND copper plane. With θ_JA = 50°C/W and 1A load at 55V→5V conversion, power dissipation is ~0.5W; junction temperature rise is ~25°C above ambient, well below the 125°C max operating limit.

Does MP4558DN-LF-P require an external bootstrap diode?

Not under typical conditions, but recommended for 2MHz operation with high duty cycles (e.g., 55V→12V). The internal bootstrap regulator may insufficiently charge the BST capacitor during short off-times; adding a Schottky diode (e.g., CMSH2-100M) from VIN to BST improves reliability and prevents driver dropout.

How does frequency fold-back improve startup safety?

During startup, frequency fold-back reduces switching frequency when inductor current approaches the current limit, preventing magnetic saturation and excessive peak currents. This lowers stress on the internal MOSFET and external diode, especially under heavy capacitive loads or short-circuit conditions.

What is the minimum output capacitor ESR requirement for stability?

No minimum ESR is required - the MP4558DN-LF-P is explicitly designed for ceramic capacitors (ESR < 10mΩ). Its current-mode architecture and transconductance error amplifier provide stable operation across zero-ESR to ~100mΩ ranges, eliminating need for tantalum or polymer alternatives.