Monolithic Power Systems Inc. MP4350DQ-LF-Z

Overview

MP4350DQ-LF-Z from Monolithic Power Systems is a 2.5A, 4MHz synchronous step-down DC/DC converter with integrated 150mΩ high-side MOSFET, 4.5V–20V input range, and 0.8V–16V adjustable output. It delivers up to 95% efficiency, features internal soft-start, frequency foldback, and thermal shutdown, and is deployed in DSL power supplies and battery-powered set-top boxes.

For engineers reviewing the MP4350DQ-LF-Z datasheet, MP4350DQ-LF-Z pinout, MP4350DQ-LF-Z application, or MP4350DQ-LF-Z equivalent, key selection criteria include its 4MHz programmable switching frequency, 100µA quiescent current for low-power operation, 10-pin QFN (3mm × 3mm) package footprint, and internal current limit without external sense resistor.

Technical Context

The MP4350DQ-LF-Z implements current-mode control with a fixed-frequency PWM architecture at up to 4MHz, using an external resistor on the FREQ pin to set oscillation frequency. Its error amplifier provides 200V/V gain and 60µA/V transconductance, enabling fast transient response and stable loop compensation via the COMP pin.

It integrates a bootstrap-regulated floating gate driver for the high-side MOSFET, with BST-to-SW UVLO (2.2V rising threshold) and internal 2.6V regulator powering core logic across the full 4.5V–20V VIN range. Startup includes 1.5ms internal soft-start ramp and 50µs glitch blanking, while shutdown is triggered by EN <1.2V, VIN UVLO (<2.6V), or junction temperature >150°C.

Key Specifications

Pinout & Package

MP4350DQ-LF-Z is housed in a thermally enhanced 10-pin QFN package (3mm × 3mm, 0.5mm pitch) with exposed thermal pad on underside for PCB heat sinking.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP2451DT-LF-Z and TPS54202DDCR, MP4350DQ-LF-Z uniquely combines 4MHz operation, 100µA I_Q, and 20V input rating-making it optimal for EMI-sensitive, battery-backed, or automotive-adjacent applications where size, efficiency, and transient robustness are co-prioritized.

Availability

MP4350DQ-LF-Z is available at Aetrix Electronics and suitable for DSL power supplies, set-top box core rails, battery-powered surveillance cameras, and automotive infotainment displays requiring stable component supply and RoHS-compliant packaging.

Supply support for MP4350DQ-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, headquartered in Kirkland, WA, with global design and support centers.

The MP4350 belongs to MPS's high-frequency buck converter product line, engineered specifically for EMI-critical, space-constrained applications such as broadband communications equipment and portable electronics requiring clean, compact, and efficient DC/DC conversion.

FAQ

What is the maximum recommended input voltage for reliable 4MHz operation?

The MP4350DQ-LF-Z supports up to 20V input per absolute maximum ratings, but for stable 4MHz operation, Monolithic Power recommends limiting VIN to ≤12V when f_SW = 4MHz (per Figure 2 in datasheet Rev. 1.0). At higher VIN, minimum on-time limitation may cause pulse-skipping; an external bootstrap diode is strongly advised above 2MHz to ensure BST capacitor recharge.

Does MP4350DQ-LF-Z require an external bootstrap diode?

No external bootstrap diode is required for operation up to 2MHz. However, at 4MHz, the internal bootstrap charging time per cycle is reduced; Monolithic Power explicitly recommends adding an external Schottky diode (e.g., CMSH3-20MA) from VIN to BST to guarantee sufficient BST voltage under all load and duty-cycle conditions.

Can MP4350DQ-LF-Z regulate output voltages below 0.8V?

No. The internal feedback reference is fixed at 0.8V ±2.4%, and the FB pin is designed to compare against this threshold. Output voltages below 0.8V cannot be regulated-designs requiring sub-0.8V outputs must use a different controller with adjustable or lower reference voltage.

How is thermal performance affected by the exposed pad connection?

The exposed thermal pad on the QFN package must be soldered to a dedicated PCB copper pour connected to GND for optimal θ_JA = 50°C/W. Leaving it unconnected degrades thermal resistance by >30%, risking thermal shutdown at >1.5A load; minimum 4×4 array of thermal vias to inner ground plane is recommended.

Is frequency foldback active during startup?

Yes. Frequency foldback operates continuously-including during startup-to prevent inductor current runaway. Combined with the 1.5ms internal soft-start and 50µs glitch blanking, this ensures controlled VOUT ramp and avoids saturation of the output inductor under heavy capacitive loads.

What is the minimum output capacitance required for stability?

The MP4350DQ-LF-Z is stable with ≥22µF ceramic output capacitance (e.g., X5R/X7R 0805 or larger). For 3.3V output, typical designs use 22–47µF; lower values risk instability if ESR is too low-compensation network (R3/C3/C6) must be adjusted per Table 3 in datasheet Rev. 1.0 for non-standard C2/L combinations.

Does EN pin support logic-level interfacing with 1.8V or 3.3V microcontrollers?

Yes. With EN rising threshold of 1.5V and falling threshold of 1.2V, the MP4350DQ-LF-Z is compatible with both 1.8V and 3.3V GPIOs. A 1.8V MCU output meets the 1.5V enable threshold; no level-shifter is needed. Internal 1µA pull-up also allows direct connection to open-drain or CMOS outputs.