Monolithic Power Systems Inc. MP171AGS-Z

Overview

MP171AGS-Z from Monolithic Power Systems is a 700V primary-side constant-voltage offline regulator with integrated MOSFET, supporting buck/boost/buck-boost/flyback topologies. It delivers up to 60mA output current in CCM, achieves <30mW no-load consumption, and features green-mode operation with frequency foldback and peak current compression for high light-load efficiency. It targets non-isolated standby power supplies in home appliances and white goods.

For engineers reviewing the MP171AGS-Z datasheet, MP171AGS-Z pinout, MP171AGS-Z application, or MP171AGS-Z equivalent, key selection criteria include its 700V drain rating, SOIC-8 package thermal resistance (θJA = 96°C/W), VFB reference of 2.55V, OLP delay of 175ms, and integrated protection suite (TSD, UVLO, SCP, OLP, open-loop detection).

Technical Context

The MP171AGS-Z implements primary-side regulation using internal sampling capacitor feedback-eliminating optocouplers-and employs a self-biased VCC supply derived from the DRAIN pin via an internal high-voltage current source. Its control architecture combines fixed-frequency PWM with adaptive green-mode behavior: switching frequency and peak current both scale down under light load to minimize no-load power.

Protection logic is fully autonomous: overload triggers a 175ms timer before latching off; short-circuit detection uses 300mA threshold with 180ns leading-edge blanking; thermal shutdown activates at 150°C with 30°C hysteresis; open-loop detection responds to FB voltage falling below 0.5V. All fault conditions initiate auto-restart after VCC discharges to 2.5V and recharges.

Key Specifications

Pinout & Package

MP171AGS-Z is housed in an SOIC-8 package with exposed pad thermal enhancement. Pin 1 is FB, Pin 2 is SOURCE, Pins 3 and 4 are SOURCE (dual-source configuration), Pin 5 is NC, Pin 6 is NC, Pin 7 is DRAIN, and Pin 8 is VCC. The dual-SOURCE pins reduce ground path impedance and improve current sensing stability.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP171AGS-Z, MP172AGS-Z offers higher power capability and surge margin but shares identical SOIC-8 footprint and control architecture, while LNK3206G trades integration for isolation compliance-making MP171AGS-Z optimal for cost-sensitive, non-isolated, sub-2W applications demanding ultra-low standby power.

Availability

MP171AGS-Z is available at Aetrix Electronics and suitable for home appliance standby power, smart thermostat power supplies, and industrial sensor node PSUs requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MP171AGS-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 power management ICs, with over 20 years of expertise in DC/DC converters, AC/DC controllers, and motor drivers.

The MP171A product line delivers highly integrated, primary-side regulated offline controllers targeting cost-sensitive, non-isolated, low-power (<2W) applications where optocoupler elimination, ultra-low standby consumption, and simplified EMI compliance are critical design goals.

FAQ

What is the minimum recommended output capacitor value for stable regulation?

The MP171AGS-Z requires a minimum 22μF output capacitor-preferably low-ESR ceramic or tantalum-to maintain loop stability and prevent oscillation during light-load conditions. Below this value, feedback sampling becomes inaccurate due to insufficient hold time on the internal sampling capacitor (C3), causing output voltage drift above 5%.

Can MP171AGS-Z operate in flyback topology with isolation?

Yes, MP171AGS-Z supports isolated flyback configurations using an auxiliary winding for feedback, but it does not provide galvanic isolation by itself-the transformer provides isolation. The IC regulates based on reflected auxiliary voltage, requiring careful turns ratio design to map VFB = 2.55V to the desired output voltage.

How does the device handle input voltage surges up to 2kV?

MP171AGS-Z withstands 2kV surges when paired with a 3.3μF input capacitor (per Table 2 in datasheet) and a 20Ω/2W fused resistor. Its 700V drain rating and internal OLP/SCP protections prevent latch-up; however, sustained surges exceeding 100ms require external MOV clamping to avoid junction overheating.

Is a dummy load required for proper regulation at no-load?

A 3mA dummy load is required to ensure sufficient inductor energy transfer for sampling capacitor (C3) charging. Without it, the FB voltage fails to reach 2.55V, causing regulation loss. For applications prioritizing lowest no-load power, a Zener diode can replace the resistor dummy load-but sacrifices light-load regulation accuracy.

What is the purpose of the dual SOURCE pins in SOIC-8 package?

The dual SOURCE pins (Pins 2 and 4) separate high-current power return from low-noise signal ground. This minimizes voltage drop across the bond wire during MOSFET switching, preventing FB reference corruption and enabling accurate current-limit detection without external sense resistors.

Does MP171AGS-Z support synchronous rectification?

No, MP171AGS-Z does not support synchronous rectification. It is designed for use with external Schottky or fast-recovery diodes (e.g., SRGC10JH). The internal control loop lacks gate-drive outputs or timing signals necessary to drive a synchronous MOSFET; adding one would require external timing circuitry and compromise the primary-side regulation accuracy.