Monolithic Power Systems Inc. MP9928GF

Overview

MP9928GF from Monolithic Power Systems is a 4V–60V input, current-mode synchronous step-down controller IC that drives dual N-channel MOSFETs to regulate output voltage in high-voltage DC/DC conversion. It features programmable 100–1000kHz switching frequency, 99.5% maximum duty cycle for low-dropout operation, and precision 0.800V ±12mV feedback reference. Used in PoE-powered devices requiring robust overvoltage (110–120% V_FB) and thermal (170°C) protection.

For engineers reviewing the MP9928GF datasheet, MP9928GF pinout, MP9928GF application, or MP9928GF equivalent, key selection considerations include its TSSOP-20-EP package, dual-gate driver capability, AAM/CCM mode selection via CCM/AAM pin, and external current limit configuration through ILIM pin status (GND/VCC1/floating).

Technical Context

The MP9928GF implements peak current-mode control with slope compensation, using cycle-by-cycle current limiting referenced to SENSE+/SENSE− with three fixed sense thresholds (25mV/50mV/75mV). Its error amplifier delivers 70dB open-loop DC gain and 500μA/V transconductance to stabilize regulation against load and line transients.

It integrates dual gate drivers with 2Ω TG pull-up, 1Ω BG pull-down, and 60ns dead time; supports external synchronization (100–1000kHz) via EN/SYNC pin; and provides 180° out-of-phase SYNCO output for multi-phase coordination. The internal VCC1 regulator accepts bias from VIN or external VCC2 (5–12V), reducing quiescent power dissipation.

Key Specifications

Pinout & Package

TSSOP-20-EP package with exposed thermal pad (pin 20 = PGND); 0.65mm pitch, 6.5mm × 4.4mm footprint. Pin mapping validated per MP9928 Rev. 1.1 datasheet, Table "PIN FUNCTIONS".

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM5116PWPR and RT7297CZSP, the MP9928GF offers superior light-load efficiency via AAM, flexible bias sourcing via VCC2, and precise current limit selection-making it optimal for PoE, DCP, and industrial applications demanding adaptability and robustness.

Availability

MP9928GF is available at Aetrix Electronics and suitable for PoE-powered devices, USB charging ports, industrial control modules, and linear charger pre-regulators requiring stable component supply across extended temperature ranges (–40°C to +125°C).

Supply support for MP9928GF 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 core expertise in DC/DC conversion, motor drivers, and LED lighting controllers.

The MP9928GF belongs to MPS's high-voltage synchronous buck controller product line, designed specifically for industrial, PoE, and automotive applications where wide input range, high efficiency, and fault resilience are critical.

FAQ

What is the minimum input voltage required for reliable startup of MP9928GF?

The MP9928GF has an input UVLO rising threshold of 4.5–5.0V; startup requires VIN ≥5.0V. Once running, it sustains operation down to 4.0V due to hysteresis (UVLO falling = 3.7–3.95V), enabling compatibility with automotive cold-crank scenarios where battery voltage dips transiently.

How does the ILIM pin configure current limit, and what are the corresponding sense voltages?

The ILIM pin selects one of three factory-trimmed current sense thresholds: tied to GND = 25mV, tied to VCC1 = 50mV, or left floating = 75mV. These correspond to peak inductor current limits of approximately 7A, 3.5A, and 2.3A respectively when used with a 0.5mΩ sense resistor.

Can MP9928GF operate without an external VCC2 supply?

Yes. When VCC2 is left open or biased below 4.45V, the internal VCC1 regulator derives power from VIN. However, supplying 5–12V to VCC2 reduces VIN current draw, lowers thermal stress, and improves overall efficiency-especially at high input voltages (>24V).

What is the purpose of the SYNCO pin, and when does it output a valid clock?

SYNCO provides a 180° out-of-phase clock signal for interleaved dual-phase operation. It outputs a valid clock only during normal CCM or DCM operation; it goes DC during hiccup mode, sleep, low-dropout operation, or fault conditions-enabling safe multi-phase coordination.

How is soft-start duration determined, and what capacitor value yields ~10ms ramp time?

Soft-start duration is set by external capacitor (C_SS) on SS pin, charged by a 2–6μA current source. Using the typical 4μA value, a 22nF capacitor yields ~10ms ramp time (t ≈ V_REF × C_SS / I_SS = 0.8V × 22nF / 4μA ≈ 4.4ms to 0.8V; full 0–V_OUT ramp is ~2× longer).

Does MP9928GF support forced continuous conduction mode (FCCM) independent of load?

No. MP9928GF does not offer true FCCM. It operates in CCM under medium-to-heavy loads and automatically transitions to AAM (pulse-skipping) at light loads when CCM/AAM pin is pulled low. CCM is enforced only when CCM/AAM is floated or tied to VCC1-no dynamic load-independent FCCM mode exists.

What is the recommended layout practice for SENSE+ and SENSE− traces?

SENSE+ and SENSE− must be routed as a tightly coupled, Kelvin-connected differential pair-minimizing loop area and avoiding noisy SW or PGND traces. Place the sense resistor close to the inductor, and route SENSE+/- directly to pins 13/14 with guard rings tied to SGND to reject common-mode noise.