Monolithic Power Systems Inc. MP4558DQ-LF-P

Overview

MP4558DQ-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 employs current-mode control for fast transient response and operates in pulse-skipping mode at light load to achieve up to 95% efficiency. Used in automotive power rails where wide VIN and EMI-sensitive AM-band compatibility are required.

For engineers reviewing the MP4558DQ-LF-P datasheet, MP4558DQ-LF-P pinout, MP4558DQ-LF-P application, or MP4558DQ-LF-P equivalent, key selection criteria include its 12µA shutdown current, internal soft-start, ceramic-capacitor stability, and bootstrap charging behavior at 2MHz operation - all critical for battery-backed industrial and automotive subsystems.

Technical Context

The MP4558DQ-LF-P implements fixed-frequency peak-current-mode PWM control with cycle-by-cycle current limiting and programmable oscillator (via external FREQ resistor). Its error amplifier features 400V/V gain and 120µA/V transconductance, driving a COMP node that directly sets MOSFET on-time via current-sense comparator.

Thermal shutdown activates at 150°C with 20°C hysteresis; under-voltage lockout engages at 3.0V rising threshold (2.6V falling); EN pin has 1.55V rising/1.2V falling thresholds with internal 1µA pull-up. Bootstrap driver regulates BST-SW voltage to ~5V using an internal PMOS charge pump and includes UVLO (2.2V rising, 150mV hysteresis).

Key Specifications

Pinout & Package

MP4558DQ-LF-P is housed in a RoHS-compliant 10-pin QFN package (3mm × 3mm, 0.5mm pitch) with exposed thermal pad. The package supports high-power dissipation (θ_JA = 50°C/W, θ_JC = 12°C/W) and requires soldering of the exposed pad to PCB ground plane for thermal and EMI performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar non-synchronous buck converter applications.

Compared with MP4558DQ-LF-P, MP4571DQ-LF-Z offers higher current capability and efficiency while maintaining pin compatibility and footprint; LM5164QPWPRQ1 trades programmability for automotive qualification and EMI robustness - making MP4558DQ-LF-P suitable only for legacy cost-sensitive industrial designs where upgrade path exists.

Availability

MP4558DQ-LF-P is available at Aetrix Electronics and suitable for automotive infotainment power, industrial PLC I/O modules, and battery-powered test equipment requiring stable component supply and long-term obsolescence management.

Supply support for MP4558DQ-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 over two decades of leadership in DC/DC conversion and motor control.

The MP4558 belongs to MPS's high-voltage buck converter product line, designed specifically for rugged industrial and automotive applications demanding wide input range, high efficiency, and reliable operation under voltage transients.

FAQ

What is the maximum allowable input voltage for MP4558DQ-LF-P?

The absolute maximum input voltage (VIN) is +60V, but the recommended operating range is 3.8V to 55V. Operation above 55V risks exceeding internal gate oxide limits and may trigger overvoltage protection or cause permanent damage. For sustained 48V rail applications, ensure transient spikes remain below 60V with appropriate clamping.

Can MP4558DQ-LF-P operate with only ceramic capacitors on input and output?

Yes - MP4558DQ-LF-P is explicitly characterized and guaranteed stable with ceramic output capacitors (≥10µF, X5R/X7R), and input ceramics (≥4.7µF). Its current-mode architecture and internal compensation eliminate the need for ESR-dependent stabilization, unlike many older voltage-mode controllers.

Why does MP4558DQ-LF-P require an external bootstrap diode at 2MHz?

At 2MHz, the minimum off-time (~100ns) and high switching duty cycles reduce time available for internal bootstrap capacitor recharge via the VIN-to-BST PMOS path. An external Schottky diode (e.g., CMSH2-100M) provides a low-loss, fast-recharge path from VIN to BST during SW low periods, preventing bootstrap undervoltage and gate drive failure.

Is MP4558DQ-LF-P pin-compatible with MP4558DN-LF-P (SOIC8E)?

No - MP4558DQ-LF-P uses a 10-pin QFN package with different pin mapping (e.g., SW on Pins 1&2, VIN on Pins 8&9), while MP4558DN-LF-P uses an 8-pin SOIC with exposed pad and merged SW/VIN functions. Footprint, thermal pad, and routing are incompatible; redesign is required for package substitution.

What happens during short-circuit condition on the output?

Under short-circuit, MP4558DQ-LF-P initiates frequency foldback and reduces current limit to ~50% of nominal (≈0.65A), lowering power dissipation. FB voltage drops near 0V, causing soft-start to reset and hold output at safe level until fault clears. Thermal shutdown activates if junction exceeds 150°C.

Does MP4558DQ-LF-P support synchronous rectification?

No - MP4558DQ-LF-P is a non-synchronous buck converter requiring an external Schottky diode for freewheeling. It lacks a low-side gate driver output or control logic for synchronous FET timing. For synchronous operation, consider MPS's MPQ4571 or MPQ4420A series.

How is the switching frequency programmed on MP4558DQ-LF-P?

Connect a resistor (RFREQ) from FREQ pin (Pin 7) to GND. Use RFREQ = (100000 / f_SW(kHz)) kΩ - e.g., 47kΩ sets f_SW ≈ 2.13MHz. Values below 40kΩ risk instability; values above 200kΩ drop frequency below 500kHz and reduce light-load efficiency.