Monolithic Power Systems Inc. MP4558DN-LF-Z

Overview

MP4558DN-LF-Z 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, 2MHz programmable switching frequency, and 140μA quiescent current-designed for automotive and industrial high-voltage power conversion where compact size and EMI-sensitive environments (e.g., AM radio band) demand high-frequency operation.

For engineers reviewing the MP4558DN-LF-Z datasheet, MP4558DN-LF-Z pinout, MP4558DN-LF-Z application, or MP4558DN-LF-Z equivalent, key selection criteria include its 55V max input rating, internal soft-start, ceramic-capacitor compatibility, frequency fold-back under light load, and thermal shutdown protection-critical for battery-powered and automotive systems requiring robust startup and fault tolerance.

Technical Context

The MP4558DN-LF-Z implements peak-current-mode control with an internal GM error amplifier (120µA/V transconductance, 400V/V gain) and programmable oscillator (set via external resistor on FREQ pin). Its current-limit threshold is internally trimmed to 1.9A typical with ±30% variation, and it features cycle-by-cycle overcurrent protection with fold-back during short-circuit conditions.

It uses a floating bootstrap driver (BST pin) to gate the high-side MOSFET, requiring external BST–SW capacitor charging during SW low periods; minimum on-time is 100ns and minimum off-time is 100ns, enabling stable operation up to 2MHz while limiting duty-cycle constraints at high VIN/VOUT ratios.

Key Specifications

Pinout & Package

MP4558DN-LF-Z is packaged in SOIC-8E (exposed pad), optimized for thermal dissipation in space-constrained PCB layouts. The exposed pad must be soldered to a GND plane for θJA = 50°C/W and reliable 1A operation at +85°C ambient.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP4558DN-LF-Z, MP4571DN-LF-Z offers higher current capability and lower quiescent power while maintaining pin compatibility, whereas LM5164QDGSRQ1 trades programmability for automotive qualification-making MP4558DN-LF-Z suitable only for legacy industrial or non-automotive replacements where cost and existing layout reuse are prioritized.

Availability

MP4558DN-LF-Z is available at Aetrix Electronics and suitable for automotive body electronics, industrial sensor transmitters, distributed telecom power, and battery-powered IoT nodes requiring stable component supply across extended temperature and voltage ranges.

Supply support for MP4558DN-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 design centers in the US, China, and Taiwan, and global manufacturing partnerships.

The MP45xx series targets high-input-voltage DC/DC conversion for automotive, industrial, and telecom applications-emphasizing integration, EMI resilience, and thermal robustness in compact packages.

FAQ

What is the maximum supported input voltage for MP4558DN-LF-Z?

The absolute maximum input voltage is +60V, but the recommended operating range is 3.8V to 55V. Operation above 55V risks exceeding internal voltage ratings of the BST regulator and gate driver, potentially causing premature failure. For sustained 55V operation, thermal derating and proper PCB copper pour on the exposed pad are essential.

Can MP4558DN-LF-Z drive a 10µH inductor at 2MHz?

Yes-its 100ns minimum on-time supports stable 2MHz operation with 10µH inductors down to ~12V input. At VIN = 12V and VOUT = 3.3V, the calculated duty cycle is ~28%, yielding sufficient on-time margin. However, layout must minimize BST–SW loop inductance to ensure reliable bootstrap charging at full frequency.

Why does MP4558DN-LF-Z require an external Schottky diode?

It is a non-synchronous buck converter with only an integrated high-side MOSFET; the low-side path relies on an external Schottky diode for freewheeling current during MOSFET off-time. A 100V/2A Schottky (e.g., B290-13-F) is recommended to handle worst-case reverse voltage and minimize conduction loss.

Is MP4558DN-LF-Z RoHS compliant and lead-free?

Yes-the "-LF" suffix explicitly denotes lead-free, RoHS-compliant packaging. All MPS devices meet RoHS Directive 2011/65/EU requirements, and the SOIC8E package uses matte tin plating with no lead content in terminations or die attach.

How does frequency fold-back improve light-load efficiency?

Below ~100mA load, MP4558DN-LF-Z reduces switching frequency proportionally to load current-lowering gate drive and switching losses while maintaining regulation. This extends battery runtime significantly versus fixed-frequency operation, especially in intermittently active IoT sensors.

What is the purpose of the COMP pin, and how is it used?

COMP is the output of the internal error amplifier and serves as the control node for loop compensation. An RC network (e.g., 68.1kΩ + 220pF) is connected between COMP and GND to set pole-zero locations, ensuring phase margin >45° and stable transient response across line/load variations.

Does MP4558DN-LF-Z support output voltages below 0.8V?

No-the internal reference is fixed at 0.800V ±20mV, and the FB pin is designed to compare against this threshold. Output voltages below 0.8V cannot be regulated; for sub-0.8V rails, a different converter with adjustable reference or external reference injection is required.