Monolithic Power Systems Inc. MP174GS-Z

Overview

MP174GS-Z from Monolithic Power Systems is a 700V primary-side constant-voltage (CV) off-line regulator with integrated MOSFET, supporting Buck, Buck-Boost, Boost, and Flyback topologies. It delivers up to 400mA output current in CCM mode, achieves <30mW no-load power consumption, and operates in green-mode with frequency foldback and peak-current compression for high light-load efficiency. It targets non-isolated low-power AC/DC conversion in home appliances and standby power supplies.

For engineers reviewing the MP174GS-Z datasheet, MP174GS-Z pinout, MP174GS-Z application, or MP174GS-Z equivalent, key selection criteria include its 700V/13.5Ω integrated MOSFET, VCC UVLO thresholds (5.1–5.3V turn-on, 5.4–5.6V turn-off), FB reference voltage (2.45–2.65V), OLP trigger at 1.7V FB, and thermal shutdown at 150°C with 30°C hysteresis.

Technical Context

The MP174GS-Z implements primary-side regulation using internal error amplifier sampling of the FB pin 6μs after MOSFET turn-off, referenced to a 2.55V internal bandgap. Its green-mode operation dynamically reduces both switching frequency and peak current limit (660mA typ → lower under light load) to maintain efficiency down to no-load.

It integrates a 700V vertical DMOS power transistor with 13.5Ω R_DS(on) at 25°C, internally biased VCC supply, and comprehensive protection including OTP (150°C), UVLO, OLP (220ms delay), SCP (900mA threshold), and open-loop detection (<0.5V FB). Leading-edge blanking (350ns on DRAIN, 180ns for SCP) suppresses false triggering from diode reverse-recovery spikes.

Key Specifications

Pinout & Package

MP174GS-Z is housed in an SOIC-8 package with exposed pad for thermal enhancement. Pin 1 is VCC, Pin 2 is FB, Pins 3 and 4 are SOURCE (internally tied), Pin 5 is N/C, Pin 6 is N/C, Pin 7 is DRAIN, and Pin 8 is N/C. The SOURCE pins serve as ground reference for VCC and FB; DRAIN connects directly to high-voltage input rail.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar primary-side off-line regulator applications.

Compared with MP174GS-Z, MP173GS-Z sacrifices 50V surge margin and light-load efficiency for lower unit cost, while LNK3206G trades primary-side simplicity for higher no-load power and reduced CV accuracy-making MP174GS-Z optimal for new designs targeting DOE Level VI compliance and compact non-isolated topologies.

Availability

MP174GS-Z is available at Aetrix Electronics and suitable for home appliance control boards, smart thermostat standby rails, and industrial sensor node auxiliary supplies requiring stable component supply across multi-year production cycles.

Supply support for MP174GS-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 core expertise in DC/DC conversion, AC/DC regulation, and motor control.

The MP174 product line delivers highly integrated primary-side regulators for cost-sensitive, non-isolated off-line power conversion - designed specifically to replace optocoupler-based solutions in white goods, consumer electronics, and industrial auxiliary supplies.

FAQ

What topologies does MP174GS-Z support, and which require isolation?

MP174GS-Z supports Buck, Buck-Boost, Boost, and Flyback topologies. Buck, Buck-Boost, and Boost are inherently non-isolated; Flyback provides galvanic isolation via transformer coupling. Isolation is determined solely by transformer implementation-not by the IC itself.

How does MP174GS-Z achieve <30mW no-load consumption?

It combines green-mode operation (reducing switching frequency and peak current under light load), internal VCC biasing, frequency foldback, and peak-current compression. At no-load, switching frequency drops below 10kHz and peak current falls to ~200mA, minimizing dynamic and static losses.

What is the role of the FB pin, and how is output voltage set?

The FB pin senses a resistor-divided sample of the output voltage. The internal 2.55V reference compares against this signal to regulate output. Output voltage is calculated as V_OUT = 2.55V × (1 + R1/R2), where R2 is typically 5kΩ–10kΩ for optimal noise immunity and bias current.

Can MP174GS-Z be used in designs requiring reinforced isolation?

No. MP174GS-Z is a primary-side controller intended for non-isolated or basic-isolation (e.g., Flyback with standard transformer) applications. It lacks the safety certification (e.g., UL 60747-5-5, VDE 0884-11) required for reinforced isolation systems.

What are the critical PCB layout considerations for MP174GS-Z?

Minimize the high-di/dt loop formed by DRAIN, SOURCE, and freewheeling diode; place a 470pF capacitor between FB and SOURCE near the IC; connect the SOIC-8 exposed pad directly to a large copper pour tied to SOURCE; and keep feedback traces short and away from noisy nodes like DRAIN and switching inductors.

Does MP174GS-Z require an external VCC capacitor, and what value is recommended?

Yes. A 1–2.2μF ceramic capacitor rated ≥16V must be placed between VCC and SOURCE, as close as possible to the IC. This capacitor sustains internal circuitry during switching cycles and must have low ESR to prevent VCC droop-induced instability.

How does the OLP protection behave during startup versus steady-state overload?

OLP triggers only after FB remains ≤1.7V for 220ms (at 28kHz switching), preventing false trips during normal startup or transient load surges. During steady-state overload, the IC enters auto-restart mode: VCC discharges to 2.4V, then recharges via internal HV regulator once below 2.4V.