Monolithic Power Systems Inc. MP157GS

Overview

MP157GS from Monolithic Power Systems is a primary-side constant-voltage (CV) off-line regulator 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 datasheet, MP157GS pinout, MP157GS application, or MP157GS equivalent, key selection criteria include its primary-side regulation architecture (no optocoupler), integrated high-voltage MOSFET, VCC UVLO thresholds (4.45V/4.6V), FB reference voltage (2.55V), and thermal shutdown at 150°C - all critical for compact, cost-sensitive offline SMPS designs.

Technical Context

The MP157GS implements primary-side CV control using feedback sampled via an internal error amplifier with 6μs delay and ramp compensation, enabling precise output regulation without secondary-side sensing. Its green-mode operation dynamically scales switching frequency and peak current (640mA typ.) with load, maintaining >75% efficiency at 10% load.

Protection logic includes timer-based OLP triggered at FB ≤1.7V for ≥150ms, SCP activation at 900–1200mA peak current, open-loop detection at FB <60mV, and auto-restart thermal shutdown at 150°C. The internal 400ns leading-edge blanking prevents false current-sense triggering during MOSFET turn-on transients.

Key Specifications

Pinout & Package

MP157GS 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 (internally tied), Pin 7 is DRAIN, and Pins 5, 6, and 8 are no-connect.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP157GS, MP158GS offers higher power headroom and robustness for demanding industrial environments, while LNK3206G trades integration for flexibility in ultra-low-cost, low-power implementations - making MP157GS the optimal balance of integration, efficiency, and ease-of-use for 4–6W applications.

Availability

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

Supply support for MP157GS 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 over 20 years of expertise in DC/DC conversion and AC/DC regulation.

The MP157 product line delivers highly integrated, energy-efficient offline regulators targeting cost-sensitive, space-constrained applications in consumer and industrial markets - emphasizing primary-side control, minimal external components, and global energy compliance.

FAQ

What topologies does MP157GS support, and which require isolation?

MP157GS supports Buck, Buck-Boost, Boost, and Flyback topologies. Only Flyback provides galvanic isolation; the others are non-isolated. Flyback implementation requires a transformer with auxiliary winding for feedback sampling, while Buck/Buck-Boost/Boost use direct feedback from the output rail.

How does MP157GS achieve no-optocoupler regulation in Flyback designs?

MP157GS samples output voltage indirectly via a resistive divider from the transformer's auxiliary winding. The FB pin monitors this sampled voltage, and internal error amplification with 6μs delay and ramp compensation maintains ±3% regulation without secondary-side components.

What is the minimum recommended output capacitor for stable 12V/350mA operation?

For stable 12V/350mA operation in CCM, a 100μF/25V low-ESR electrolytic capacitor is recommended (per Figure 12). Ceramic or tantalum capacitors may be added in parallel to reduce high-frequency ripple below 50mVpp.

Can MP157GS operate with universal input (85–265VAC) without derating?

Yes - MP157GS is rated for universal input operation. At 265VAC, maximum output is 6W; at 85VAC, output is limited to ~4W due to reduced input voltage headroom and increased conduction losses in the integrated MOSFET.

What thermal management is required for continuous 6W operation in SOIC-8?

For continuous 6W operation, the SOIC-8 package requires the exposed DRAIN pad to be soldered to ≥4cm² of 2oz copper on the PCB's inner layer, achieving θ_JA ≤96°C/W. Without this, thermal shutdown will activate above 4W at 25°C ambient.

How does the 400ns leading-edge blanking affect layout sensitivity?

The 400ns LEB suppresses false overcurrent trips caused by parasitic ringing at MOSFET turn-on. Layout must minimize source inductance - keep SOURCE pins directly connected to ground plane with short, wide traces - otherwise LEB may mask genuine fault conditions.

Is MP157GS RoHS-compliant and halogen-free?

Yes - MP157GS is lead-free, halogen-free, and fully compliant with the EU RoHS Directive 2011/65/EU. Full material declarations and test reports are available on the MPS Quality Assurance portal.