Monolithic Power Systems Inc. MP157GS-P

Overview

MP157GS-P from Monolithic Power Systems is a primary-side constant-voltage (CV) off-line regulator IC with integrated 500V/10Ω MOSFET, supporting Buck, Buck-Boost, Boost, and Flyback topologies. It delivers up to 6W output power, achieves <100mW no-load consumption, and operates in green mode with frequency foldback and peak current compression for high light-load efficiency. It targets low-power AC/DC conversion in home appliance standby supplies.

For engineers reviewing the MP157GS-P datasheet, MP157GS-P pinout, MP157GS-P application, or MP157GS-P equivalent, this page provides verified topology support, protection thresholds (e.g., VFB_OLP = 1.7V, TSD = 150°C), package-specific thermal resistance (SOIC-8 θJA = 96°C/W), and real-world design constraints including minimum off-time (13.1μs) and SCP trigger level (900mA).

Technical Context

The MP157GS-P implements primary-side regulation using feedback sampling via an internal error amplifier with 6μs delay and ramp compensation that scales exponentially with load-3mV/μs at full load-to maintain precise CV accuracy without optocouplers. Its green-mode control dynamically reduces both switching frequency and peak current under decreasing load, enabling stable operation down to no-load while maintaining >75% average efficiency.

Protection architecture includes timer-based Over Load Protection (150ms delay at 37kHz), cycle-by-cycle Short Circuit Protection (900mA threshold), open-loop detection (<60mV FB), and auto-restart Thermal Shutdown (150°C). The internal 400ns leading-edge blanking prevents false current-sense triggering during MOSFET turn-on transients.

Key Specifications

Pinout & Package

MP157GS-P is housed in an SOIC-8 package with exposed pad connected to DRAIN for 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 not connected.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP157GS-P, MP158GS-Z offers +1W headroom and tighter regulation but identical footprint and protection set, while LNK3206G sacrifices integration and power capability for legacy ecosystem alignment-making MP157GS-P the optimal balance of integration, efficiency, and design simplicity for new 6W-class applications.

Availability

MP157GS-P is available at Aetrix Electronics and suitable for home appliance standby power, industrial sensor node supplies, and IoT gateway auxiliary rails requiring stable component supply across multi-year production cycles.

Supply support for MP157GS-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 core expertise in DC/DC conversion, LED drivers, and motor control.

The MP157 belongs to MPS's primary-side regulation product line, engineered specifically for cost-sensitive, space-constrained offline AC/DC converters needing optocoupler-free CV accuracy and green-mode efficiency compliance.

FAQ

What topologies does MP157GS-P support, and which require isolation?

MP157GS-P supports Buck, Buck-Boost, Boost, and Flyback topologies. Only Flyback provides galvanic isolation between input and output; the other three are non-isolated and require careful safety spacing in end equipment. Flyback implementation uses indirect feedback via auxiliary winding, while Buck/Buck-Boost/Boost use direct output sampling.

How does MP157GS-P achieve constant voltage regulation without an optocoupler?

It uses primary-side regulation: an internal error amplifier samples the reflected output voltage across an RC network tied to the FB pin. Ramp compensation and 6μs delayed sampling correct for transformer leakage and load-dependent variations, achieving ±5% CV accuracy across line/load/temperature without secondary-side components.

What is the maximum continuous output current for MP157GS-P in CCM operation?

In Continuous Conduction Mode, MP157GS-P supports a maximum output current of less than 360mA. This is constrained by its 640mA typical peak current limit, minimum off-time (13.1μs), and thermal limits in SOIC-8 (θJA = 96°C/W); actual achievable current depends on inductor value, input voltage, and heatsinking.

Does MP157GS-P include over-temperature protection, and how does it behave?

Yes-it features thermal shutdown at 150°C with auto-restart. When junction temperature exceeds 150°C, switching halts and the internal HV current source discharges VCC to ~2.4V before recharging. This cycle repeats until temperature falls below hysteresis threshold, preventing permanent damage without requiring manual reset.

Can MP157GS-P operate with universal AC input (85–265VAC)?

Yes-its integrated 500V MOSFET and internal HV start-up circuit enable direct operation from rectified universal AC input. Design examples confirm stable 12V/350mA output across 85–265VAC with appropriate input capacitor selection (e.g., 10μF/400V per rail) and surge protection components.

What is the purpose of the 400ns leading-edge blanking (LEB) function?

The 400ns LEB disables the current-sense comparator immediately after MOSFET turn-on to suppress false triggering caused by parasitic ringing and transformer leakage spikes. This ensures accurate peak-current limiting and prevents premature switch-off during high-dV/dt transitions.

How does the green-mode operation improve light-load efficiency?

Green-mode dynamically reduces both switching frequency and peak current as load decreases. At no-load, frequency drops significantly and peak current compresses from 640mA toward minimum-reducing switching losses, gate drive losses, and core losses simultaneously to sustain <100mW input power.