Monolithic Power Systems Inc. MP173GS-P

Overview

MP173GS-P from Monolithic Power Systems is a 700 V non-isolated offline primary-side constant-voltage regulator with integrated MOSFET, supporting buck/boost/buck-boost/flyback topologies. It delivers up to 280 mA output current in CCM mode, achieves <30 mW no-load power consumption, and operates across -40°C to +125°C junction temperature. It targets low-power offline applications including appliance standby supplies and white-goods auxiliary power rails.

For engineers reviewing the MP173GS-P datasheet, MP173GS-P pinout, MP173GS-P application, or MP173GS-P equivalent, key selection criteria include its primary-side CV control architecture, 700 V integrated MOSFET breakdown rating, green-mode frequency foldback behavior, and SOIC-8 package thermal resistance (θ_JA = 96 °C/W).

Technical Context

The MP173GS-P implements primary-side regulation using feedback sampling via an external capacitor (C3) charged during freewheeling diode conduction, eliminating optocoupler dependency. Its internal error amplifier compares FB voltage to a 2.55 V reference and adjusts switching duty via peak-current limiting and minimum off-time control.

Green-mode operation dynamically reduces both peak current limit (from 420 mA down to ~160 mA) and switching frequency under light load, enabling <30 mW no-load consumption. Protection logic includes auto-restart OLP (220 ms delay), SCP (600 mA threshold), TSD (150°C trip), and open-loop detection (V_FB < 0.5 V).

Key Specifications

Pinout & Package

MP173GS-P is housed in an SOIC-8 package with exposed thermal pad connected to SOURCE pins. Pin 1 is VCC (IC supply), Pin 2 is FB (voltage feedback input), Pins 3 and 4 are SOURCE (MOSFET source and ground reference), Pin 7 is DRAIN (HV MOSFET drain), and Pins 5, 6, and 8 are NC (no connection).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar non-isolated offline regulator applications.

Compared with MP173GS-P, MP173A-GS-P offers tighter regulation and newer qualification, while LNK304DG requires optocoupler-based feedback and delivers higher no-load consumption-making MP173GS-P uniquely suited for cost-sensitive, non-isolated, ultra-low-standby applications.

Availability

MP173GS-P is available at Aetrix Electronics and suitable for home appliance standby supplies, white-goods auxiliary power, and consumer electronics adapters requiring stable component supply and long-term industrial availability.

Supply support for MP173GS-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 core expertise in DC/DC conversion, LED drivers, and motor control.

The MP173 product line delivers primary-side regulated offline controllers targeting cost-sensitive, non-isolated AC/DC applications where optocoupler elimination and ultra-low standby power are critical design goals.

FAQ

What topology configurations does MP173GS-P support?

MP173GS-P supports buck, boost, buck-boost, and flyback topologies in non-isolated implementations. Its primary-side CV control architecture uses a sampling capacitor (C3) to hold output voltage during freewheeling, enabling regulation without optocouplers. The datasheet provides validated schematics and component values for each configuration, including high-side buck and flyback variants with auxiliary winding feedback.

How does MP173GS-P achieve <30 mW no-load power consumption?

MP173GS-P achieves <30 mW no-load consumption through green-mode operation: both switching frequency and peak current limit decrease under light load. At no load, frequency drops below 10 kHz and peak current compresses to ~160 mA, reducing switching and conduction losses. Internal VCC consumption drops to 200 µA in no-switching mode, and the 16 µA latch-off discharge current minimizes residual draw during fault recovery.

What is the role of the sampling capacitor (C3) in MP173GS-P feedback?

The sampling capacitor (C3) serves as a hold capacitor that captures and retains the output voltage during the freewheeling diode conduction phase. It is charged to V_OUT when D1 conducts, then slowly discharges into the FB resistor divider. This allows the internal error amplifier to sample V_OUT without secondary-side components, enabling precise primary-side CV regulation with typical accuracy of ±5% across line and load.

Can MP173GS-P be used in isolated flyback designs?

Yes, MP173GS-P can be used in isolated flyback topologies by connecting the FB pin to an auxiliary winding on the transformer. In this configuration, the auxiliary voltage reflects the output voltage, allowing primary-side regulation without optocoupler. The datasheet specifies auxiliary winding turns ratio calculation and includes layout guidance to minimize leakage inductance impact on regulation accuracy.

What thermal considerations apply to MP173GS-P in SOIC-8 package?

In SOIC-8, MP173GS-P has θ_JA = 96 °C/W and θ_JC = 45 °C/W on a 4-layer PCB per JESD51-7. For 1 W dissipation at 25°C ambient, junction temperature reaches ~121°C - within the 150°C absolute max. To ensure reliability, connect SOURCE pins to ≥2 cm² copper pour, avoid routing high-dv/dt traces near FB, and maintain ≥0.5 mm clearance between DRAIN and other nets per IPC-2221B creepage requirements.

Why is MP173GS-P marked "Not Recommended for New Designs"?

MP173GS-P is marked "Not Recommended for New Designs" because Monolithic Power Systems introduced the MP173A-GS-P as its functional successor with improved EMI performance, tighter V_FB tolerance (±0.5% vs. ±0.1 V), and enhanced protection timing. MP173GS-P remains fully qualified and supported for legacy production and repair, but new designs should adopt MP173A-GS-P to align with current qualification standards and long-term supply assurance.