Monolithic Power Systems Inc. MP174GJ-P

Overview

MP174GJ-P 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 appliance standby supplies.

For engineers reviewing the MP174GJ-P datasheet, MP174GJ-P pinout, MP174GJ-P application, or MP174GJ-P equivalent, key selection criteria include its 700V/13.5Ω integrated MOSFET, 2.55V FB reference voltage, 12–15μs minimum off-time, thermal shutdown at 150°C, and TSOT23-5 package compatibility with space-constrained designs.

Technical Context

The MP174GJ-P implements primary-side regulation using internal error amplifier sampling and ramp compensation, eliminating optocoupler dependency. Its feedback loop monitors output voltage via a sampling capacitor and regulates by adjusting switching on-time based on a 2.55V reference threshold at the FB pin.

It employs green-mode operation: both switching frequency and peak current limit decrease under light load, enabled by internal timing control and peak-current compression logic. Protection functions-including OLP (220ms delay), SCP (900mA threshold), OTP (150°C), UVLO (5.3V turn-on), and open-loop detection (0.5V FB threshold)-are implemented in hardware with auto-restart behavior.

Key Specifications

Pinout & Package

MP174GJ-P is housed in a 5-pin TSOT23-5 package with exposed drain pad for thermal enhancement. Pin 1 is VCC, Pin 2 is FB, Pins 3 and 4 are SOURCE (internally tied), and Pin 5 is DRAIN. No pins are NC in this variant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP174GJ-P, MP173GJ-Z trades 100mA output headroom for marginal cost reduction, while LNK304DG-TL increases design effort and reduces light-load efficiency due to lack of integrated regulation and green-mode features.

Availability

MP174GJ-P is available at Aetrix Electronics and suitable for home appliance standby supplies, smart thermostat power rails, and industrial sensor node auxiliary power requiring stable component supply, RoHS-compliant packaging, and long-term lifecycle support.

Supply support for MP174GJ-P 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 two decades of leadership in DC/DC, AC/DC, and motor drive solutions.

The MP174 product line delivers highly integrated primary-side regulators targeting cost-sensitive, space-constrained off-line power applications where optocoupler elimination and ultra-low standby power are critical design goals.

FAQ

What topologies does MP174GJ-P support, and which require external components?

MP174GJ-P supports Buck, Buck-Boost, Boost, and Flyback topologies. All require an external inductor, freewheeling diode, and output capacitor. Flyback adds a transformer; Buck-Boost and Boost require negative output handling or floating ground design. No external current-sense resistor or optocoupler is needed in any configuration.

How does MP174GJ-P achieve <30mW no-load power consumption?

It combines green-mode operation-reducing switching frequency and peak current under light load-with internal VCC biasing from the DRAIN pin and low-quiescent ICC (200μA in no-switching mode). The 2.55V FB reference and ramp compensation further minimize regulation overhead at near-zero load.

What is the role of the two SOURCE pins (3 and 4) in TSOT23-5 package?

Pins 3 and 4 are internally bonded together as the MOSFET source terminal and serve as the common ground reference for VCC and FB circuits. They must be connected to the same low-impedance power ground plane to ensure accurate feedback sensing and stable internal biasing.

Can MP174GJ-P be used in isolated Flyback designs, and how is regulation achieved?

Yes-it supports isolated Flyback via indirect feedback using a resistive divider from secondary-side output to primary-side FB pin through an auxiliary winding. Regulation relies on transformer coupling accuracy and the 2.55V FB threshold; no optocoupler is required, but transformer turns ratio must be precisely matched to target voltage.

What thermal considerations apply to MP174GJ-P in TSOT23-5 package?

With θ_JA = 100°C/W, the TSOT23-5 package dissipates up to 1W at 25°C ambient. For continuous 5W output, PCB copper area under the exposed DRAIN pad and thermal vias are essential. Derate power linearly above 25°C; thermal shutdown activates at 150°C junction temperature.

How does OLP protection trigger, and what is the recovery behavior?

OLP triggers when FB voltage falls below 1.7V for 220ms (at 28kHz switching), indicating sustained overload. The IC stops switching, discharges VCC via 16μA current source, and restarts automatically once VCC drops to 2.4V and recovers to 5.3V-no manual reset required.

Is MP174GJ-P compatible with universal AC input (85–265VAC)?

Yes-its 700V MOSFET and internal HV startup circuit support universal AC input. Input capacitor sizing must follow MPS recommendations: 3μF/W for half-wave rectification (≤2W) or 1.5–2μF/W for full-wave (≥2W), ensuring minimum DC bus stays above 70V to avoid thermal stress.