Monolithic Power Systems Inc. MP38873DL-LF-Z

Overview

MP38873DL-LF-Z from Monolithic Power Systems is a 15A, 16V synchronous step-down DC-DC converter with integrated high-side MOSFET and external low-side gate driver. It delivers 15A continuous output from 4.5–16V input, supports 0.8–12V adjustable output, and operates at fixed 400kHz or externally synchronized 300kHz–1MHz. Used in PCB space-constrained distributed power systems.

For engineers reviewing the MP38873DL-LF-Z datasheet, MP38873DL-LF-Z pinout, MP38873DL-LF-Z application, or MP38873DL-LF-Z equivalent, key selection criteria include its 25mΩ internal high-side R_DS(ON), cycle-by-cycle current limiting, thermal shutdown at 150°C, programmable soft-start, and phase-shift synchronization capability via SYNCIN/SYNCOUT.

Technical Context

The MP38873DL-LF-Z implements peak-current-mode control with a fixed 400kHz oscillator or external synchronization up to 1MHz. Its error amplifier compares FB voltage against a 0.810V reference (±2% accuracy) and drives the COMP node to regulate duty cycle via current-sense feedback.

It integrates a 5V internal VCC regulator powered from VIN, drives an external low-side MOSFET via GATE pin with 1Ω sink / 4Ω source impedance, and uses bootstrap charging (BST pin) for high-side gate drive. UVLO triggers at 4.1V rising threshold with 900mV hysteresis.

Key Specifications

Pinout & Package

MP38873DL-LF-Z is housed in a thermally enhanced 20-pin 3mm × 4mm QFN package with exposed thermal pad (pins 10 and 18 tied to VIN, pin 20 to GND). The package supports high-power density layouts and requires solder paste stencil optimization for thermal pad reflow.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP38873DL-LF-Z, MP2315DJ-LF-Z trades output current and synchronization for compactness and cost, while RTQ2132B-QT adds digital intelligence at the expense of analog simplicity and pin compatibility-making MP38873DL-LF-Z optimal for high-current, analog-synchronized, space-constrained buck designs.

Availability

MP38873DL-LF-Z is available at Aetrix Electronics and suitable for telecom point-of-load regulation, FPGA core supplies, industrial motor drive logic, and compact DC-DC pre-regulators requiring stable component supply across extended production cycles.

Supply support for MP38873DL-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 MP38873 belongs to MPS's high-current synchronous buck converter product line, engineered specifically for space-constrained, high-efficiency DC-DC conversion in telecom infrastructure, computing, and industrial automation.

FAQ

What is the minimum recommended output capacitor ESR for stable operation?

The MP38873DL-LF-Z is optimized for low-ESR ceramic output capacitors and does not require a minimum ESR for stability. Its current-mode control architecture allows stable operation with ESR as low as 1mΩ. For ceramic capacitors, output ripple is dominated by capacitive reactance-not ESR-so total capacitance (e.g., ≥100µF) is more critical than ESR value.

Can the MP38873DL-LF-Z operate without an external low-side MOSFET?

No. The MP38873DL-LF-Z integrates only a high-side power MOSFET and requires an external N-channel MOSFET connected to the GATE and SW pins to complete the synchronous buck topology. Omitting the external MOSFET disables synchronous rectification and causes immediate failure due to body-diode conduction losses and thermal overload.

How is the 15A current rating validated-peak or RMS?

The 15A rating is a continuous DC output current specification verified under worst-case conditions: T_A = +85°C, 4-layer JEDEC PCB, 12V input, 1.2V output, and proper thermal layout including soldered exposed pad. It reflects RMS current handling capability-not peak pulse current-and assumes adequate input/output capacitance and inductor saturation margin.

Does the SYNCIN pin require a pull-up or pull-down resistor when unused?

Yes. When SYNCIN is unused, it must be tied directly to VCC (not left floating) to disable external synchronization and enable the internal 400kHz oscillator. Leaving SYNCIN unconnected risks erratic frequency behavior due to noise coupling, as the pin has 10nA bias current and TTL-compatible thresholds (2V high, 0.4V low).

What is the purpose of the BST capacitor, and what value is recommended?

The BST capacitor (0.1–1µF ceramic) forms a floating voltage source between SW and BST pins to drive the internal high-side MOSFET gate above VIN. Its value balances gate charge delivery and AC coupling effectiveness: 0.22µF is typical for 12V input, while 0.47µF improves robustness at lower input voltages (e.g., 5V). Placement must be within 2mm of BST/SW pins.

Is the PG pin actively driven or open-drain?

The PG pin is strictly open-drain. It pulls low when V_OUT falls outside the ±10% regulation window (i.e., <90% or >110% of target); otherwise, it remains high-impedance. A mandatory 100kΩ pull-up resistor to VCC or VOUT is required to generate a valid logic-high signal for power sequencing controllers.

How does the SS/TRK pin function in tracking mode versus soft-start mode?

In soft-start mode, SS/TRK is connected to ground via a capacitor charged by the internal 8µA current source, controlling output ramp rate. In tracking mode, an external voltage (e.g., from another regulator's VOUT) is applied directly to SS/TRK, forcing the MP38873's output to follow that reference-enabling precise multi-rail sequencing without additional ICs.