Monolithic Power Systems Inc. MP38891DL-LF-Z

Overview

MP38891DL-LF-Z from Monolithic Power Systems is a synchronous step-down DC/DC converter with integrated 50mΩ high-side MOSFET and external gate driver for low-side FET control, delivering 6A continuous output current across 4.5V–30V input, fixed 420kHz switching frequency (synchronizable to 1.4MHz), and adjustable 0.8V–15V output voltage - deployed in flat-panel TV power rails and broadband communication line cards.

For engineers reviewing the MP38891DL-LF-Z datasheet, MP38891DL-LF-Z pinout, MP38891DL-LF-Z application, or MP38891DL-LF-Z equivalent, this page delivers verified package mapping (3×4mm QFN-14), confirmed thermal shutdown (150°C), cycle-by-cycle overcurrent protection (8A typical), PG indicator behavior, and synchronizable EN/SYNC interface timing - all critical for industrial SMPS layout and BOM validation.

Technical Context

The MP38891DL-LF-Z implements peak-current-mode control with a fixed 420kHz oscillator, supporting external synchronization up to 1.4MHz via the EN/SYNC pin's rising-edge alignment. Its internal 5V VCC regulator powers bias circuitry across full VIN range and enables stable gate drive for external low-side MOSFETs.

Functional blocks include a 40× error amplifier referenced to 0.808V (±1.6% tolerance), cycle-by-cycle current sensing with 20mV trip threshold, hiccup-mode recovery under short-circuit, and bootstrap charging circuitry that maintains BST voltage ≥2.2V with 150mV hysteresis - ensuring robust synchronous rectification down to 65% duty cycle.

Key Specifications

Pinout & Package

MP38891DL-LF-Z is housed in a thermally enhanced 3mm × 4mm, 14-pin QFN package with exposed thermal pad (JEDEC MO-229 VGED-3). The package supports ≤45°C/W junction-to-ambient thermal resistance on 4-layer PCBs with adequate copper pour under the exposed pad.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous buck controller applications.

Compared with MP2451DT-LF-Z, MP38891DL-LF-Z delivers double the current with external FET control for optimized efficiency; versus LM5116MH/NOPB, it reduces component count and layout risk by integrating the high-side switch and VCC regulator - making it ideal for cost-sensitive 6A industrial SMPS.

Availability

MP38891DL-LF-Z is available at Aetrix Electronics and suitable for flat-panel display power, broadband line card design, digital set-top box development, and personal video recorder production requiring stable component supply across extended temperature ranges and long lifecycle commitments.

Supply support for MP38891DL-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 MP38891 belongs to MPS's synchronous buck controller product line, engineered for high-current, wide-input industrial and consumer power conversion where efficiency, thermal resilience, and EMI control are critical design constraints.

FAQ

What is the minimum recommended output capacitance for stable operation?

The MP38891DL-LF-Z is optimized for ceramic output capacitors ≥10µF with low ESR. Stability is maintained across 10–100µF range; use ≥22µF for 6A loads to limit output ripple to <20mV peak-to-peak. Tantalum or electrolytic caps require ≥5mΩ ESR for phase margin - not recommended unless ceramic is unavailable.

Does the EN/SYNC pin support both enable/disable and frequency synchronization simultaneously?

No - EN/SYNC operates in two mutually exclusive modes. Pulling the pin below 0.4V disables the IC; pulling above 1.2V enables fixed-frequency operation. Synchronization only occurs when an external clock signal (300kHz–1.4MHz) is applied while the pin is biased at ~2V - requiring external AC coupling or level-shifting circuitry.

How does the bootstrap circuit maintain gate drive during 100% duty cycle?

The MP38891DL-LF-Z cannot achieve true 100% duty cycle due to minimum off-time (~135ns) and bootstrap recharge requirement. When V_IN – V_OUT ≥3V, the internal bootstrap diode charges C_BST during SW low phase. For high-duty applications (e.g., 5V out from 5.5V in), an external Schottky diode from V_OUT to BST is recommended per Figure 3.

What is the maximum allowable PCB trace length between FB and the output resistor divider?

FB trace length must be ≤5mm with guard ring grounded to GND. Longer traces introduce noise coupling and phase shift, risking instability. Place R1/R2 within 2mm of FB pin and route feedback path over solid GND plane - never parallel to SW or IN traces. Use 1% tolerance resistors for <±1% output error.

Can the MP38891DL-LF-Z operate with input voltage below 4.5V?

No - the UVLO rising threshold is 4.10V (typical), and the internal VCC regulator requires ≥4.5V to sustain 5V bias for gate drive. Operation below 4.5V causes intermittent shutdown; for sub-4.5V inputs, consider the MPQ4470-AEC1 (3.8V min) or redesign with pre-regulation stage.

Is the exposed thermal pad electrically connected to GND internally?

Yes - the exposed pad is internally bonded to GND and must be soldered to a dedicated thermal land connected to ≥4cm² internal or external GND copper. Do not float or connect to other nets; insufficient thermal pad soldering increases θ_JA by >15°C/W and risks thermal shutdown at 4A load.

What happens to the PG pin during hiccup-mode operation?

During hiccup mode, PG remains low continuously - it does not pulse. PG asserts low when V_OUT drops below 740mV (90% of 0.808V × R1/R2 ratio) and stays latched low until V_OUT recovers above 780mV (740mV + 40mV hysteresis) for >100µs after a successful startup attempt.