Monolithic Power Systems Inc. MP171AGS-P

Overview

MP171AGS-P from Monolithic Power Systems is a 700V primary-side offline regulator IC with integrated MOSFET, delivering up to 60mA output current in CCM and supporting buck/boost/buck-boost/flyback topologies. It provides optocoupler-free constant voltage regulation, achieves <30mW no-load power consumption, and features green-mode operation for high light-load efficiency - used in non-isolated standby power supplies for home appliances.

For engineers reviewing the MP171AGS-P datasheet, MP171AGS-P pinout, MP171AGS-P application, or MP171AGS-P equivalent, key selection criteria include its 700V drain rating, VCC UVLO thresholds (5.1–5.8V), 2.55V FB reference, thermal shutdown at 150°C, and SOIC-8 package compatibility with PCB layout-sensitive high-voltage switching designs.

Technical Context

The MP171AGS-P implements primary-side CV control using internal error amplifier sampling 6µs after MOSFET turn-off, with ramp compensation scaling exponentially with load to improve regulation. Its green-mode operation dynamically reduces both peak current limit (down to ~105mA) and switching frequency under light load via frequency foldback and peak current compression.

Protection logic integrates auto-restart OLP (175ms delay), SCP (300mA threshold), open-loop detection (0.5V FB threshold), and thermal shutdown (150°C trip, 30°C hysteresis), all coordinated through a VCC-supply-dependent state machine that discharges VCC to 2.5V before restart.

Key Specifications

Pinout & Package

MP171AGS-P is housed in an industry-standard SOIC-8 package with exposed pad for 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 for high-frequency current return.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP171AGS-P, MP172AGS-P offers higher voltage headroom and better EMI performance at the cost of slightly higher quiescent current, while LNK3206P trades regulation precision and integration for broader legacy ecosystem support and lower unit cost in high-volume consumer applications.

Availability

MP171AGS-P is available at Aetrix Electronics and suitable for home appliance standby power, white goods control logic, and industrial sensor node power requiring stable component supply across extended product lifecycles.

Supply support for MP171AGS-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 power management ICs, with over 20 years of expertise in DC/DC converters, LED drivers, and offline regulators.

The MP171A product line targets cost-sensitive, space-constrained non-isolated offline power conversion, emphasizing integration, EMI robustness, and regulatory compliance for global consumer and industrial markets.

FAQ

What is the maximum recommended output power for MP171AGS-P in continuous conduction mode?

The MP171AGS-P supports up to 2W output power in CCM, validated at 5V/50mA with 230VAC input. This limit arises from its 105mA peak current limit and 700V drain rating. Exceeding 2W risks triggering OLP or exceeding thermal limits in SOIC-8 packaging without forced airflow or copper pour.

Can MP171AGS-P operate in flyback topology with primary-side regulation?

Yes - MP171AGS-P supports flyback topology using indirect feedback via a sampling capacitor (C3) on the secondary side. The device regulates output by monitoring reflected voltage across the auxiliary winding, enabling isolation without optocoupler. MPS Application Note AN-109 confirms this configuration with 1:10 turns ratio and 22nF sampling capacitor.

How does the green-mode operation reduce no-load power consumption?

Green-mode operation reduces no-load power by dynamically lowering both switching frequency and peak current limit as load decreases. At no-load, frequency drops below 30kHz and peak current compresses toward 105mA, minimizing switching losses and gate drive energy. Combined with <200µA internal IC consumption in no-switching state, total no-load draw stays below 30mW.

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

The dual SOURCE pins (Pins 2 and 3) provide parallel low-inductance paths for high di/dt return current from the internal MOSFET. This reduces ground bounce and improves EMI performance in high-frequency switching. They must be tied together externally to a solid ground plane - splitting them degrades regulation stability and increases radiated emissions.

Does MP171AGS-P require an external VCC capacitor, and what value is recommended?

Yes - a 10µF/25V electrolytic or 22µF/16V tantalum capacitor is recommended between VCC and SOURCE. This capacitor sustains internal circuitry during MOSFET on-time when the HV current source is inactive. Smaller values (<4.7µF) risk premature UVLO dropout under transient loads; larger values increase start-up time but improve hold-up during line dips.

How does open-loop detection function, and what triggers it?

Open-loop detection triggers when FB voltage falls below 0.5V (VOLD), indicating loss of feedback signal - e.g., open resistor divider or failed sampling capacitor. The IC stops switching and initiates auto-restart after discharging VCC to 2.5V. Detection is blanked for first 512 cycles to prevent false trips during start-up with large output capacitors.