Monolithic Power Systems Inc. MP38115DQ-LF-P

Overview

MP38115DQ-LF-P from Monolithic Power Systems is a 1.5MHz fixed-frequency, synchronous step-down DC/DC regulator delivering up to 4A output current from 1.1V–5.5V input, regulating down to 0.8V with integrated 60mΩ high- and low-side MOSFETs. It supports µP/FPGA core supplies, features power-good output, frequency synchronization, and operates in a 3mm × 3mm QFN10 package.

For engineers reviewing the MP38115DQ-LF-P datasheet, MP38115DQ-LF-P pinout, MP38115DQ-LF-P application, or MP38115DQ-LF-P equivalent, key selection criteria include its 1.5MHz switching frequency, internal soft-start (120µs), hiccup short-circuit protection, thermal shutdown (150°C), and compatibility with all-ceramic capacitor designs for compact point-of-load solutions.

Technical Context

The MP38115DQ-LF-P implements peak-current-mode PWM control with internal Type II compensation, eliminating external compensation components while enabling stable loop bandwidth tuning via FB resistor selection. Its transconductance gain of 11.25A/V links COMP voltage directly to inductor peak current.

It integrates dual 60mΩ MOSFETs, uses bootstrap gate drive (BS pin) for high-side N-channel operation, and provides cycle-by-cycle current limiting (6.5A high-side / 3.5A low-side). EN/SYNC serves as both enable input (1.6V turn-on, 0.4V shutdown) and 1–2MHz synchronization interface.

Key Specifications

Pinout & Package

MP38115DQ-LF-P is housed in a thermally enhanced 3mm × 3mm, 10-lead QFN package with exposed thermal pad on underside. Pin numbering follows JEDEC MO-229 VEED-5 standard; pins 4 & 7 are parallel IN inputs, pins 3 & 8 are parallel SW nodes, and pins 2 & 9 are GND connections to minimize high-current loop inductance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP2147 and MP2315, the MP38115DQ-LF-P uniquely combines 4A capability, internal compensation, power-good output, and frequency synchronization in a single 3mm × 3mm QFN - making it optimal for high-density, multi-rail systems requiring deterministic timing and minimal BOM count.

Availability

MP38115DQ-LF-P is available at Aetrix Electronics and suitable for FPGA I/O rail generation, ASIC core supply, and LCD TV T-Con power delivery requiring stable component supply across extended temperature ranges (–40°C to +85°C).

Supply support for MP38115DQ-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 MP38115 belongs to MPS's ultra-low-voltage synchronous buck regulator product line, designed specifically for high-current, space-constrained point-of-load applications in computing, telecom, and consumer electronics where efficiency, integration, and thermal performance are critical.

FAQ

What is the recommended input capacitor configuration for MP38115DQ-LF-P?

Two 22µF X5R/X7R ceramic capacitors are required-one placed adjacent to each IN pin (pins 4 and 7)-with short, wide traces to GND pins (2 and 9). This dual-input configuration reduces high-frequency switching current loop area and suppresses VIN ripple below 10mV p-p at 4A load.

Can MP38115DQ-LF-P operate with an output voltage lower than 0.8V?

No. The internal feedback reference is fixed at 0.800V ±2%, and the datasheet specifies a minimum output voltage of 0.8V. Output voltages below this threshold are not supported or guaranteed; attempting to set VOUT < 0.8V results in regulation failure and potential instability.

Is an external Schottky diode required for reliable operation?

An external Schottky diode (e.g., B0530) is recommended when output current exceeds 2A to clamp negative voltage spikes at the SW node and improve efficiency by ~1–2%. It is not mandatory for ≤2A loads but strongly advised for 4A operation to ensure robustness under transient conditions.

How does the EN/SYNC pin behave when used for synchronization versus enable control?

When used for synchronization, a clean 1–2MHz square wave applied to EN/SYNC overrides the internal oscillator; the part starts switching after detecting 3–4 valid clock edges. If the clock duty cycle causes any ON/OFF period >4µs, the pin reverts to enable mode, potentially disabling the device unexpectedly.

What is the thermal performance of the QFN10 package under 4A continuous load?

With a 4-layer PCB per JESD51-7, θ_JA = 50°C/W. At 4A output with 3.3V_IN/1.2V_OUT, typical power dissipation is ~0.45W, resulting in ~22.5°C junction-to-ambient rise. Full derating begins above 125°C junction temperature, well within the 150°C thermal shutdown threshold.

Does MP38115DQ-LF-P support pre-biased output startup?

Yes. During startup, if the output is pre-biased above the target VOUT, the IC disables both high- and low-side switches until the internal soft-start capacitor voltage exceeds the sensed FB voltage. This prevents reverse current flow and ensures monotonic output ramp-up.

Why does the datasheet state "Not Recommended for New Designs"?

MPS issued this notice because MP2147 offers improved efficiency, smaller footprint, and updated process technology. However, MP38115DQ-LF-P remains fully qualified, in active production, and supported for legacy designs, second-sourcing, and applications requiring its specific feature set (e.g., 4A + SYNC + PG in QFN10).