Monolithic Power Systems Inc. MP173GS-Z

Overview

MP173GS-Z 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 such as appliance standby supplies and white-goods auxiliary power rails.

For engineers reviewing the MP173GS-Z datasheet, MP173GS-Z pinout, MP173GS-Z application, or MP173GS-Z equivalent, key selection criteria include its primary-side CV control architecture, 700 V integrated MOSFET breakdown rating, SOIC-8 package thermal resistance (96°C/W θJA), green-mode frequency foldback behavior, and OLP/SCP/TSD protection thresholds confirmed in electrical characterization.

Technical Context

The MP173GS-Z implements primary-side regulation using internal error amplifier sampling of a feedback capacitor (C3) voltage 6 µs after MOSFET turn-off, referenced to a 2.55 V internal bandgap. Its green-mode operation dynamically reduces both peak current limit (420 mA → down to ~160 mA) and switching frequency under light load via programmable off-time extension.

Protection logic includes auto-restart OLP triggered at FB ≤1.74 V for ≥220 ms, SCP activation at peak current ≥600 mA with 180 ns leading-edge blanking, and thermal shutdown at 150°C with 30°C hysteresis. The IC self-starts from DRAIN via internal HV regulator and maintains VCC between 5.1 V (turn-on) and 5.7 V (turn-off).

Key Specifications

Pinout & Package

MP173GS-Z is housed in an SOIC-8 package with exposed pad thermal enhancement. Pin 1 is VCC (control supply), Pin 2 is FB (feedback input), Pins 3 and 4 are SOURCE (MOSFET source and ground reference), Pin 7 is DRAIN (integrated 700 V 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 primary-side offline regulator applications.

Compared with MP173A-GS-Z, MP173GS-Z has slower OLP response and looser VFB accuracy, making it unsuitable for high-precision or fast-transient applications; versus LNK304DG-TL, it eliminates optocoupler dependency but requires stricter layout for EMI control due to primary-side sensing.

Availability

MP173GS-Z is available at Aetrix Electronics and suitable for home appliance standby supplies, industrial sensor auxiliary power, and consumer electronics AC-DC adapters requiring stable component supply throughout extended product lifecycles.

Supply support for MP173GS-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 design centers in the US, China, and Taiwan.

The MP173 product line delivers highly integrated primary-side offline regulators targeting ultra-low-no-load-power, non-isolated AC-DC conversion for cost-sensitive, space-constrained applications in white goods and consumer electronics.

FAQ

What topologies does MP173GS-Z support?

MP173GS-Z supports buck, boost, buck-boost, and flyback configurations without external HV components. Its primary-side CV control eliminates optocouplers in all four topologies. The SOIC-8 package's DRAIN pin connects directly to rectified AC input, enabling simplified board layout and reduced bill-of-materials count compared to controller-only solutions.

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

MPS explicitly designates MP173GS-Z as obsolete for new designs in favor of MP173A-GS-Z, which features faster OLP response (120 ms vs 220 ms), tighter VFB tolerance (±0.5% vs ±1%), and enhanced ESD robustness (4 kV HBM). The original MP173 remains available for legacy repair and replacement but lacks updated qualification for newer safety and efficiency standards.

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

It combines green-mode operation-reducing switching frequency and peak current under light load-with internally biased VCC and low ICC (200 µA in no-switching state). The 700 V MOSFET's low leakage (17 µA at 400 V) and frequency foldback below 10 kHz minimize dynamic losses, enabling compliance with DOE Level VI and EU CoC Tier 2 standby power limits.

What is the maximum output power achievable with MP173GS-Z?

In continuous conduction mode (CCM), MP173GS-Z delivers up to 4 W output power with proper inductor selection (e.g., 1.2 mH) and thermal management. At 250 mA output current and 12 V, it sustains 3 W with <50°C junction rise on a 4-layer PCB. Derating is required above 85°C ambient due to SOIC-8's 96°C/W θJA.

Can MP173GS-Z be used in isolated flyback designs?

Yes-MP173GS-Z supports isolated flyback topologies using indirect feedback via an auxiliary winding. The IC regulates output by sampling the auxiliary winding voltage during MOSFET off-time, eliminating the need for optocoupler-based secondary-side feedback. Design Example in MPS datasheet Rev. 1.01 confirms stable 12 V/250 mA isolation with <±3% regulation.

What are the critical PCB layout guidelines for MP173GS-Z?

Minimize the high-di/dt loop formed by DRAIN, SOURCE, and freewheeling diode; place feedback capacitor (C3) within 2 mm of FB/SOURCE pins; use a 100–470 pF capacitor directly across FB-SOURCE; connect the SOIC-8 exposed pad to DRAIN net for thermal relief; and avoid routing sensitive analog traces near DRAIN or inductor nodes to prevent false triggering of protection circuits.

How does the open-loop protection function in MP173GS-Z?

When FB voltage falls below 0.5 V (indicating feedback network failure or severe overload), MP173GS-Z halts switching and initiates automatic restart after VCC discharges to 2.5 V. During soft-start, this protection is blanked for 256 cycles to prevent false triggering. Recovery occurs only after VCC recharges to 5.5 V and FB rises above 0.5 V.