Monolithic Power Systems Inc. MP158GS

Overview

MP158GS from Monolithic Power Systems is a primary-side constant-voltage (CV) off-line regulator with integrated 500V MOSFET, supporting Buck, Buck-Boost, Boost, and Flyback topologies. It delivers up to 2W output power, achieves <30mW no-load consumption, and operates across –40°C to +125°C junction temperature for home appliance standby supplies and low-power industrial controls.

For engineers reviewing the MP158GS datasheet, MP158GS pinout, MP158GS application, or MP158GS equivalent, this page provides verified topology support, green-mode frequency foldback behavior, thermal shutdown recovery hysteresis, VCC UVLO thresholds, and SOIC-8 package-specific thermal resistance data required for reliable offline AC/DC design.

Technical Context

The MP158GS implements primary-side regulation using internal error amplifier sampling and ramp compensation, eliminating optocoupler dependency. Its feedback comparator triggers at 2.55V reference with 6μs delay after MOSFET turn-off, enabling accurate CV control in non-isolated and isolated configurations.

Green-mode operation dynamically reduces switching frequency and peak current under light load: minimum off-time is 7.4–11.7μs, peak current limit compresses from 101mA (typ) down to ~10mA at standby, and OLP initiates after 120ms if FB falls below 1.7V-ensuring stable regulation without external timing components.

Key Specifications

Pinout & Package

MP158GS is housed in an SOIC-8 package with exposed pad thermal enhancement, rated for 1W continuous power dissipation at T_A = 25°C (θ_JA = 96°C/W, θ_JC = 45°C/W). Pin 1 is VCC; pins 3 and 4 are SOURCE (common ground reference); pin 7 is DRAIN; pin 2 is FB; pins 5, 6, and 8 are NC.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP157GS, MP158GS adds 100V headroom for robust universal AC operation and 0.5W extra output capacity; versus LNK304DG, it eliminates optocoupler dependency and cuts no-load power by 70%, directly reducing system-level standby certification risk.

Availability

MP158GS is available at Aetrix Electronics and suitable for smart home appliance control, industrial sensor node power, and white goods auxiliary supply requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.

Supply support for MP158GS 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.

The MP158 product line targets ultra-low-power offline AC/DC conversion, emphasizing primary-side regulation, green-mode efficiency, and compact packaging for cost-sensitive consumer and industrial applications.

FAQ

What topologies does MP158GS support and which require isolation?

MP158GS supports Buck, Buck-Boost, Boost, and Flyback topologies. Buck, Buck-Boost, and Boost are non-isolated and provide direct feedback; Flyback is isolated and uses indirect feedback via transformer-coupled sampling. Isolation is achieved only in Flyback configuration using appropriate transformer turns ratio and safety-rated Y-capacitors.

How does MP158GS achieve <30mW no-load power consumption?

MP158GS achieves <30mW no-load power through three coordinated mechanisms: frequency foldback (reducing switching frequency at light load), peak-current compression (scaling ILimit down to ~10mA), and ultra-low 16μA latch-off current that discharges VCC slowly. These features minimize both dynamic and quiescent losses without external bias circuitry.

What is the role of the FB pin and how is output voltage set?

The FB pin senses output voltage via a resistor divider and compares it to an internal 2.55V reference. Output voltage is set by R1 and R2 using V_OUT = 2.55V × (1 + R1/R2). R2 is typically 5–10kΩ; values above 100kΩ degrade light-load regulation due to leakage current effects on the sampled voltage.

Does MP158GS require an external dummy load and why?

Yes - a 1–2mA dummy load is required to maintain sufficient inductor energy for the sampling capacitor (C3) to hold output voltage during MOSFET off-time. Without it, light-load regulation degrades because the FB pin cannot accurately sample V_OUT; however, zener diode-based dummy loads can be used to minimize no-load power penalty.

What thermal considerations apply to MP158GS in SOIC-8 package?

In SOIC-8, MP158GS has θ_JA = 96°C/W and θ_JC = 45°C/W on a 4-layer PCB. For 1W dissipation at 25°C ambient, junction temperature reaches ~121°C - within 150°C limit but requires adequate copper pour under the exposed pad. Thermal shutdown activates at 150°C with 30°C hysteresis, ensuring safe auto-recovery.

Can MP158GS replace MP158GJ in the same design?

Yes - MP158GS (SOIC-8) and MP158GJ (TSOT23-5) share identical electrical specifications and functional block diagram. However, SOIC-8 offers higher power dissipation (1W vs. 1W but with lower θ_JA), better thermal performance, and easier hand-soldering. Layout and thermal pad design must be updated to match SOIC-8 footprint and pinout.