Monolithic Power Systems Inc. MP172GS-Z

Overview

MP172GS-Z from Monolithic Power Systems is a 700 V primary-side constant-voltage (CV) regulator with integrated MOSFET, supporting buck/boost/buck-boost/flyback topologies for non-isolated off-line power supplies. It delivers up to 120 mA output current in CCM, achieves <30 mW no-load consumption, and operates across -40°C to +125°C junction temperature. It targets low-power standby and home appliance auxiliary supplies.

For engineers reviewing the MP172GS-Z datasheet, MP172GS-Z pinout, MP172GS-Z application, or MP172GS-Z equivalent, key selection criteria include its 700 V drain-source rating, 2.55 V internal FB reference, frequency foldback behavior, thermal shutdown at 150°C, and SOIC-8 package compatibility with legacy board layouts.

Technical Context

The MP172GS-Z implements green-mode operation via simultaneous reduction of switching frequency and peak current under light load, enabling high average efficiency. Its primary-side CV regulation eliminates optocoupler dependency by sampling output voltage through a dedicated feedback capacitor (C3) during freewheeling diode conduction.

Protection logic integrates auto-restart OLP (175 ms delay), SCP (400 mA threshold), TSD (150°C trip with 30°C hysteresis), and open-loop detection (VFB < 0.5 V). Start-up uses an internal HV regulator sourcing from DRAIN, with VCCON/VCCOFF hysteresis (5.5 V / 5.7 V) and latch-off discharge via 20 μA current source.

Key Specifications

Pinout & Package

MP172GS-Z is housed in an SOIC-8 package with exposed pad thermal enhancement. Pin 1 is VCC, Pin 2 is FB, Pins 3 and 4 are SOURCE (common ground reference), Pin 7 is 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 primary-side offline regulator applications.

Compared with MP172GS-Z, MP172A-GS-Z offers tighter regulation and certified design support, while LNK304DG-TL trades regulation smoothness for lower BOM cost-neither provides identical green-mode frequency foldback behavior.

Availability

MP172GS-Z is available at Aetrix Electronics and suitable for home appliance auxiliary supplies, white goods control boards, industrial sensor node power, and smart plug standby power requiring stable component supply and legacy design continuity.

Supply support for MP172GS-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, headquartered in Kirkland, Washington, with global design and support centers.

The MP172 product line delivers primary-side regulated offline power solutions targeting cost-sensitive, low-power (<3 W) applications where optocoupler elimination and green-mode efficiency are critical design goals.

FAQ

What is the recommended minimum output capacitor value for MP172GS-Z in a 5 V/120 mA buck application?

For stable regulation and ripple suppression, use ≥47 μF low-ESR electrolytic or ceramic capacitor. The datasheet specifies 47 μF (C6 in Figure 9) with 22 nF (C1) for high-frequency filtering. Smaller values risk poor light-load regulation due to insufficient hold time on the sampling capacitor.

Can MP172GS-Z operate without an external dummy load?

No. A minimum 3 mA dummy load is required to maintain sufficient inductor energy for sampling capacitor (C3) charging and accurate FB voltage detection. Removing it causes open-loop fault triggering (VFB < 0.5 V) and shutdown, especially at no-load or light-load conditions.

Why does MP172GS-Z specify two different maximum output currents (80 mA and 120 mA)?

The 80 mA limit applies to discontinuous conduction mode (DCM), where energy transfer per cycle is lower and peak current is capped. The 120 mA limit applies to continuous conduction mode (CCM), enabled by higher inductance and heavier loading-both values are measured at 230 VAC input and 25°C ambient per datasheet Table 1.

How does the internal leading-edge blanking (LEB) function protect MP172GS-Z?

LEB disables the current comparator for 350 ns after MOSFET turn-on to ignore parasitic turn-on spikes from diode reverse recovery and layout inductance. This prevents false overcurrent shutdown during normal switching transitions, ensuring reliable operation in noisy high-voltage environments.

Is MP172GS-Z RoHS-compliant and halogen-free?

Yes. MP172GS-Z is lead-free, halogen-free, and fully compliant with the EU RoHS Directive 2011/65/EU. MPS confirms green status via its Quality Assurance portal, and the device carries the "RoHS Compliant" marking on its top-side laser etch (MP172 + lot code + year/week).

What is the purpose of the NC pins (5, 6, 8) in the SOIC-8 package?

Pins 5, 6, and 8 are internally unconnected and must remain floating-no PCB traces, vias, or solder should contact them. They exist for mechanical symmetry and thermal pad alignment in the SOIC-8 mold; connecting them risks latch-up or parametric shift due to stray capacitance or leakage paths.

Does MP172GS-Z support flyback topology with primary-side regulation?

Yes. In flyback configuration, MP172GS-Z uses indirect feedback: the sampling capacitor (C3) charges during secondary-side freewheeling, allowing primary-side regulation without optocoupler. The datasheet confirms this in Table 1 and Figure 9's flyback schematic, though isolation requires proper transformer design and creepage/clearance compliance.