Monolithic Power Systems Inc. MP158GS-Z

Overview

MP158GS-Z 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-enabling compact, low-cost standby power supplies in home appliances and white goods.

For engineers reviewing the MP158GS-Z datasheet, MP158GS-Z pinout, MP158GS-Z application, or MP158GS-Z equivalent, key selection criteria include its green-mode frequency foldback, VCC UVLO hysteresis (250mV), 2.55V FB reference accuracy, and thermal shutdown with 30°C recovery hysteresis-critical for reliable light-load efficiency and fault resilience in non-isolated AC/DC converters.

Technical Context

The MP158GS-Z implements primary-side regulation via internal error amplifier sampling the FB pin 6µs after MOSFET turn-off, referencing a 2.55V threshold to control switching cycles without optocoupler feedback. Its green-mode operation dynamically reduces both peak current (down to ~101mA – 1µA/µs × τ_off) and switching frequency under decreasing load.

Protection logic integrates timer-based overload detection (120ms delay at 50kHz), short-circuit protection (SCP threshold 220mA typ), open-loop detection (<60mV FB), and thermal shutdown (150°C trip, 120°C recovery). The IC uses leading-edge blanking (350ns for current sense, 180ns for SCP) to suppress turn-on spikes during high dv/dt transitions.

Key Specifications

Pinout & Package

MP158GS-Z is housed in an SOIC-8 package with exposed pad thermal enhancement. Pin functions are validated per MPS datasheet Rev. 1.0: VCC (Pin 2) supplies control circuitry; FB (Pin 3) senses output voltage via resistor divider; SOURCE (Pins 4 & 5) serves as MOSFET source and ground reference; DRAIN (Pin 7) connects to HV input and integrated 500V MOSFET drain; Pins 1, 6, and 8 are NC.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP157GS-Z, MP158GS-Z adds 150V MOSFET headroom and open-loop protection for universal-input reliability; versus LNK304DG, it eliminates optocoupler dependency and cuts no-load power by >60%, reducing heat and enabling smaller enclosures.

Availability

MP158GS-Z is available at Aetrix Electronics and suitable for home appliance control boards, smart thermostat standby rails, and industrial sensor node power supplies requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for MP158GS-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, and Taiwan, and global distribution through authorized partners.

The MP158 product line targets cost-sensitive, space-constrained off-line AC/DC conversion-delivering integrated primary-side regulation for sub-2W applications where simplicity, efficiency, and reliability outweigh secondary-side precision requirements.

FAQ

What topologies does MP158GS-Z support, and which require isolation?

MP158GS-Z supports Buck, Buck-Boost, Boost, and Flyback topologies. Only Flyback provides galvanic isolation via transformer coupling; the other three are non-isolated and require careful layout separation between primary and secondary circuits to meet safety standards.

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

It combines green-mode operation-reducing both switching frequency and peak current at light load-with an integrated 500V MOSFET eliminating external drive losses, low VCC operating current (165µA), and frequency foldback that extends MOSFET off-time to minimize switching losses.

Can MP158GS-Z operate without an external dummy load?

No. A minimum dummy load (~2mA) is required to maintain sufficient inductor energy for the sampling capacitor to hold output voltage during regulation. Removing it degrades light-load regulation and may trigger open-loop protection below 60mV FB voltage.

What is the role of the 6µs delay before FB sampling?

This delay allows freewheeling diode reverse recovery and parasitic ringing to settle after MOSFET turn-off, ensuring accurate sampling of the true output voltage on the feedback capacitor-critical for stable CV regulation without optocoupler feedback path errors.

How does the internal ramp compensation improve load regulation?

Ramp compensation injects a load-dependent slope into the current-sense comparator threshold, counteracting the natural reduction in loop gain at higher duty cycles. This stabilizes the control loop across 0–100% load, reducing output voltage deviation from ±5% to ±2% typical.

Is MP158GS-Z suitable for 230VAC universal-input applications?

Yes. Its 500V integrated MOSFET and validated operation up to 145VAC RMS (≈205V peak) provide sufficient margin for 230VAC ±10% inputs. Designers must verify input capacitor surge rating and inductor saturation current for full-range operation.