Monolithic Power Systems Inc. MP156GS-P

Overview

MP156GS-P from Monolithic Power Systems is a primary-side, off-line switching regulator IC with integrated 500V/20Ω MOSFET, supporting Buck, Buck-Boost, Boost, and Flyback topologies. It delivers up to 4W output power, achieves <30mW no-load consumption, and provides constant voltage regulation without opto-coupler-enabling compact, low-cost AC/DC supplies for home appliance standby power.

For engineers reviewing the MP156GS-P datasheet, MP156GS-P pinout, MP156GS-P application, or MP156GS-P equivalent, this device is selected for primary-side CV control in non-isolated and isolated low-power SMPS where light-load efficiency, thermal robustness, and minimal external component count are critical design requirements.

Technical Context

The MP156GS-P implements green-mode operation: both peak current limit (290mA typ) and switching frequency decrease under light load to maintain high efficiency down to no-load. Its internal high-voltage current source enables self-startup from the DRAIN pin, eliminating auxiliary winding requirements.

It uses primary-side feedback via the FB pin with a 2.55V ±0.1V reference, combined with minimum off-time limiting (18μs), leading-edge blanking (350ns), and ramp compensation to stabilize regulation across load and line variations. Protection logic includes timer-based OLP (170ms delay at 37kHz), SCP (450mA threshold), and thermal shutdown at 150°C with auto-restart.

Key Specifications

Pinout & Package

MP156GS-P is housed in an SOIC-8 package with exposed DRAIN pad connected internally to Pin 7. The package supports 1W continuous power dissipation at +25°C ambient (θJA = 96°C/W) and features RoHS-compliant lead-free finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP156GS-P, MP157GS-Z offers enhanced surge resilience and slightly higher power capability in identical SOIC-8 packaging, while LNK304DG trades primary-side simplicity for tighter regulation at the cost of added components and reduced light-load efficiency.

Availability

MP156GS-P is available at Aetrix Electronics and suitable for home appliance standby power, IoT edge device auxiliary rails, and industrial HMI panel supplies requiring stable component supply, long-lifecycle support, and RoHS-compliant sourcing.

Supply support for MP156GS-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 design centers in the US, China, and Taiwan, and global manufacturing partnerships.

The MP156 belongs to MPS's primary-side offline regulator product line, engineered specifically for cost-sensitive, space-constrained AC/DC applications where optocoupler elimination, ultra-low standby power, and robust protection are mandatory.

FAQ

What topologies does MP156GS-P support, and which require isolation?

MP156GS-P supports Buck, Buck-Boost, Boost, and Flyback topologies. Only Flyback provides galvanic isolation; the other three are non-isolated configurations. Flyback implementation requires an isolated transformer and feedback winding sampling, while Buck/Buck-Boost/Boost use direct primary-side sensing via the FB pin and do not require isolation components.

How is no-load power kept below 30mW?

The MP156GS-P achieves <30mW no-load consumption through coordinated green-mode operation: switching frequency folds back and peak current limit compresses as load decreases. Combined with low quiescent ICC (165µA in no-switching mode) and internal 350ns leading-edge blanking to minimize false triggering, it sustains ultra-low idle draw without external bias windings.

Can MP156GS-P operate without an external VCC capacitor?

No. An external VCC capacitor (typically 1–10µF ceramic) is mandatory. The IC uses an internal high-voltage current source from the DRAIN pin to charge this capacitor during startup and fault recovery. Without it, the VCC rail cannot sustain internal logic operation, causing immediate UVLO shutdown or erratic behavior.

What is the purpose of the N/C pins in SOIC-8 package?

Pins 5, 6, and 8 in the SOIC-8 package are designated No-Connect (N/C) and must remain unconnected on the PCB. They are electrically isolated from internal circuitry and serve only mechanical or thermal roles-no routing, stitching, or grounding is permitted, as per MPS package documentation and layout guidelines.

How does open-loop protection trigger, and what happens afterward?

Open-loop protection activates when FB voltage drops below 60mV for more than 128 switching cycles (blanked during startup). Upon detection, the IC stops switching, discharges VCC to 2.4V via 16µA current source, then recharges VCC via the internal HV supply to initiate auto-restart-ensuring recovery from broken feedback paths without manual intervention.

Is MP156GS-P compatible with universal AC input (85–265VAC)?

Yes. With its 500V integrated MOSFET and internal HV startup circuit, MP156GS-P supports universal AC input directly. Input rectification and bulk capacitance must be sized per application-e.g., ≥10μF for 1kV surge immunity-but no external HV startup resistors or auxiliary windings are needed.

What is the maximum recommended output current in CCM mode?

In continuous conduction mode (CCM), the MP156GS-P supports maximum output current less than 220mA. This limit derives from peak current limit (290mA typ), minimum off-time (18μs), and inductor selection. Exceeding this risks OLP activation or thermal overload, especially at high line voltages or elevated ambient temperatures.