Monolithic Power Systems Inc. MP8756GD-Z

Overview

MP8756GD-Z from Monolithic Power Systems is a synchronous step-down DC/DC converter delivering 6A continuous output current with adaptive constant-on-time (COT) control, 700kHz switching frequency, and 117µA quiescent current. It operates from 4.5V to 26V input, regulates output down to 0.6V, and integrates high- and low-side MOSFETs (R_DS(ON) = 30mΩ / 15mΩ) for high-efficiency power conversion in space-constrained laptop and tablet PC power rails.

For engineers reviewing the MP8756GD-Z datasheet, MP8756GD-Z pinout, MP8756GD-Z application, or MP8756GD-Z equivalent, key selection criteria include its ultrasonic mode (USM) for audible-noise-free light-load operation, DC auto-tune loop for ±1% reference accuracy under line/load variation, integrated power-good (PG) open-drain signal, and QFN-12 (2mm×3mm) thermal performance (θ_JA = 70°C/W).

Technical Context

The MP8756GD-Z employs adaptive COT control with internal ramp compensation and DC auto-tune feedback correction-enabling stable regulation with ceramic or POSCAP output capacitors without external compensation. Its valley-current OCP uses the low-side MOSFET's R_DS(ON) for cycle-by-cycle protection at 9–12A.

Ultrasonic Mode (USM) activates when MODE is floating, dynamically shrinking on-time to maintain switching above 20kHz during light load; PFM/PWM mode selection is implemented via MODE pin logic thresholds (0.4V/1.2–1.9V/2.6V), while EN enables full-cycle soft-start and output discharge via an internal 6Ω FET.

Key Specifications

Pinout & Package

MP8756GD-Z is housed in a thermally enhanced QFN-12 package (2mm × 3mm, 0.5mm pitch) with exposed thermal pad (PGND-connected) for low θ_JA (70°C/W) and high-power density mounting.

Key Features

Applications

Equivalent & Alternatives

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

Compared with RT7295BGJ8F and TPS546B24RVFT, MP8756GD-Z offers superior light-load acoustic performance via USM, simpler layout due to integrated MOSFETs and internal compensation, and optimal balance of size, efficiency, and cost for volume consumer electronics.

Availability

MP8756GD-Z is available at Aetrix Electronics and suitable for laptop computer, tablet PC, and flat-panel television power supply designs requiring stable component supply, RoHS-compliant packaging, and long-term production continuity.

Supply support for MP8756GD-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 over 20 years of leadership in DC/DC conversion and motor control.

The MP8756 belongs to MPS' high-current monolithic buck converter product line, designed specifically for space-constrained, high-efficiency computing and consumer electronics power rails demanding low I_Q, fast transient response, and robust protection.

FAQ

What is the recommended input capacitor configuration for MP8756GD-Z?

A minimum 22µF X7R ceramic capacitor placed within 3mm of VIN and PGND pins is required, supplemented by a bulk electrolytic (≥100µF) if input source impedance exceeds 50mΩ. Layout must use wide traces and multiple vias to minimize loop inductance and prevent voltage spikes during high di/dt switching events.

How does the DC auto-tune loop improve regulation accuracy?

The DC auto-tune loop continuously adjusts the internal reference comparator threshold to force V_FB to match 600mV, compensating for DC errors from resistor divider drift, PCB trace resistance, and temperature-induced MOSFET R_DS(ON) shifts-achieving ±1% output accuracy across full line/load/temperature range without manual calibration.

Can MP8756GD-Z operate with a 0.68µH inductor at 6A output?

Yes-the datasheet specifies 0.68µH (3.1mΩ DCR) as the standard inductor for 1V/6A operation. Peak inductor current remains below 12A OCP threshold, and saturation current rating must exceed 8.5A to ensure margin under worst-case VIN=4.5V, VOUT=1V transients.

What is the purpose of the VOUT pin, and how should it be routed?

VOUT is a dedicated Kelvin sense node for output voltage feedback, separate from PGND. It must be routed as a narrow, shielded trace ≥25mil wide, avoiding proximity to SW and power planes, with no vias-ensuring accurate regulation by eliminating IR drop errors from high-current PGND paths.

Does MP8756GD-Z support pre-biased output startup?

Yes-it detects pre-biased outputs during EN assertion and disables both HS- and LS-FET switching until the internal reference voltage ramps above the sensed V_FB level, preventing reverse current flow and ensuring monotonic startup without output voltage overshoot.

How is ultrasonic mode (USM) enabled and verified in layout?

USM activates automatically when MODE pin is left floating (high-impedance). To verify, measure SW node with oscilloscope during light load: frequency must remain ≥20kHz, and burst-mode intervals must show consistent 20–40µs off-periods before next on-pulse-confirming audible-noise suppression.

What thermal derating applies above +85°C ambient?

At +85°C ambient, maximum continuous output current reduces to 5.2A (derated 13%) based on θ_JA=70°C/W and T_J(MAX)=125°C. Above +100°C, output current must be limited to ≤4.0A to maintain junction temperature below 125°C with standard 4-layer PCB cooling.