Monolithic Power Systems Inc. MP157GS-Z

Overview

MP157GS-Z 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-Z datasheet, MP157GS-Z pinout, MP157GS-Z application, or MP157GS-Z equivalent, key selection criteria include its primary-side regulation architecture eliminating optocouplers, 500V drain rating, SOIC-8 package thermal performance (θJA = 96°C/W), and built-in protections including OLP (150ms timer), SCP (900mA threshold), and TSD (150°C).

Technical Context

The MP157GS-Z implements primary-side CV control using feedback sampling via an internal 2.55V reference and FB pin voltage monitoring-no secondary-side sensing or optocoupler required. Its green-mode operation dynamically scales switching frequency and peak current (640mA typ.) downward under light load to maintain >75% average efficiency.

Protection logic includes timer-based Over Load Protection triggered when FB falls below 1.7V for ≥150ms (at 37kHz), short-circuit shutdown at 900mA sensed peak current, and thermal shutdown with auto-restart at 150°C junction temperature. Internal leading-edge blanking (400ns) prevents false current-sense triggering.

Key Specifications

Pinout & Package

MP157GS-Z is housed in a standard SOIC-8 package (9.6 mm × 6.0 mm × 1.75 mm), with exposed pad connected to DRAIN for enhanced thermal dissipation (θJC = 45°C/W). The package supports reflow soldering per JESD22-A113 and is RoHS-compliant, halogen-free, and lead-free.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LNK304DG and UCC28910DR, MP157GS-Z uniquely combines 6W capability, integrated 500V MOSFET, and green-mode operation in SOIC-8-offering the lowest component count and highest light-load efficiency for cost-driven consumer and white-goods designs.

Availability

MP157GS-Z is available at Aetrix Electronics and suitable for home appliance control logic, industrial sensor interface supplies, and white goods standby power requiring stable component supply, full traceability, and long-term lifecycle support.

Supply support for MP157GS-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 analog and power ICs, with design centers in the US, China, Korea, and Taiwan.

The MP157 product line delivers compact, energy-efficient primary-side offline regulators targeting cost-sensitive, low-power AC/DC conversion in consumer, industrial, and appliance markets-emphasizing integration, efficiency, and safety compliance.

FAQ

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

MP157GS-Z supports Buck, Buck-Boost, Boost, and Flyback topologies. Only Flyback provides galvanic isolation via a transformer; the other three are non-isolated configurations. For safety-critical applications like medical or Class II consumer devices, Flyback is mandatory to meet creepage and isolation voltage requirements (e.g., 3kV RMS).

How does MP157GS-Z achieve primary-side constant voltage regulation without an optocoupler?

MP157GS-Z samples output voltage indirectly through a "sample-and-hold" capacitor charged via the freewheeling diode path. During the MOSFET OFF period, this capacitor retains a voltage proportional to the output, which is fed back to the FB pin. Internal circuitry compares it to a precise 2.55V reference to adjust duty cycle-eliminating optocoupler latency and aging drift.

What is the minimum recommended inductor value for 12V/350mA operation in CCM mode?

For 12V/350mA continuous conduction mode (CCM) operation, the minimum inductance is 1.2mH, as validated in the MP157 Rev. 1.04 datasheet Figure 8 and Typical Application Circuit (Figure 12). Using <1.2mH risks entering discontinuous mode at full load, causing output voltage instability and increased ripple.

Can MP157GS-Z be used with universal AC input (85–265VAC), and what input capacitor value is required?

Yes-MP157GS-Z supports universal AC input. With full-wave rectification, use 1.5–2μF/W of input capacitance (e.g., 10μF for 6W). For surge immunity: 10μF/400V per leg passes 1000V surge testing; dual 10μF caps plus MOV enable 2kV compliance per Figure 10.

What is the purpose of the N/C pins (5, 6, 8) in the SOIC-8 package, and how should they be handled on PCB?

Pins 5, 6, and 8 are internally unconnected and must remain electrically floating-no traces, vias, or solder mask openings should contact them. PCB land patterns must isolate these pads completely; connecting them risks latch-up or parametric shift due to stray coupling into sensitive analog blocks.

How does the thermal shutdown mechanism recover after activation?

Upon reaching 150°C junction temperature, MP157GS-Z halts switching and discharges the VCC capacitor via a 16μA internal current source until VCC drops to 2.35V (VCC_pro). The internal HV regulator then recharges VCC from the DRAIN pin. Full restart occurs once VCC rises above 4.45V (VCC_ON), enabling autonomous recovery without external intervention.

Is MP157GS-Z compliant with modern energy efficiency standards like DOE Level VI and EU CoC Tier 2?

Yes-its <100mW no-load consumption and >75% average efficiency across 10–100% load meet both DOE Level VI and EU CoC Tier 2 requirements. Performance is verified per IEC 62301 Ed.2 test conditions using the EV157-S-00A evaluation board referenced in the datasheet.