Monolithic Power Systems Inc. MP156GS-Z

Overview

MP156GS-Z from Monolithic Power Systems is a primary-side constant-voltage (CV) off-line regulator with integrated 500V/20Ω MOSFET, supporting Buck, Buck-Boost, Boost, and Flyback topologies. It delivers up to 4W output power, achieves <30mW no-load consumption, and operates across -40°C to +125°C junction temperature - enabling compact, low-cost standby power supplies for home appliances and white goods.

For engineers reviewing the MP156GS-Z datasheet, MP156GS-Z pinout, MP156GS-Z application, or MP156GS-Z equivalent, key selection criteria include its green-mode frequency foldback, 2.55V ±0.1V feedback reference, 150°C thermal shutdown threshold, and dual-package availability (SOIC8/TSOT23-5) for layout flexibility in space-constrained AC/DC designs.

Technical Context

The MP156GS-Z implements primary-side regulation using internal sampling capacitor feedback to eliminate optocouplers and secondary-side sensing circuitry. Its error amplifier compensates VFB 6µs after MOSFET turn-off, maintaining 2.55V reference accuracy across load and temperature.

Green-mode operation dynamically scales peak current (290mA typ → down to ~260mA) and switching frequency (up to 37kHz → lower under light load) via minimum off-time control (18µs normal, soft-starting from 72µs), enabling high average efficiency without auxiliary winding or external bias supply.

Key Specifications

Pinout & Package

MP156GS-Z is housed in an industry-standard SOIC8 package (5.0mm × 6.2mm × 1.75mm), optimized for thermal dissipation (θ_JA = 96°C/W) and automated assembly. Exposed DRAIN pin connects to large copper pour for enhanced heat transfer.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP157GS-Z, MP156GS-Z offers lower no-load power and tighter VFB tolerance but reduced HV margin; versus LNK304DG, it eliminates optocoupler dependency and simplifies transformer design at the cost of slightly lower peak power capability.

Availability

MP156GS-Z is available at Aetrix Electronics and suitable for smart home power supplies, appliance standby controllers, and industrial sensor transmitters requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MP156GS-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 manufacturing partnerships.

The MP156 product line targets cost-sensitive, space-constrained off-line AC/DC conversion in consumer and industrial applications, emphasizing primary-side regulation, ultra-low standby power, and multi-topology flexibility without external sensing components.

FAQ

What topologies does MP156GS-Z support, and which require isolation?

MP156GS-Z supports Buck, Buck-Boost, Boost, and Flyback topologies. Buck, Buck-Boost, and Boost are non-isolated configurations with direct input-to-output connection; Flyback provides galvanic isolation via transformer coupling and is the only topology that meets safety standards requiring reinforced insulation between primary and secondary sides.

How does MP156GS-Z achieve <30mW no-load power consumption?

MP156GS-Z achieves <30mW no-load consumption through green-mode operation: frequency foldback reduces switching losses, peak-current compression lowers conduction loss, and internal 16μA latch-off current minimizes VCC discharge rate. No external dummy load is required when using recommended feedback capacitor and resistor values.

What is the function of the N/C pins in the SOIC8 package?

Pins 6 and 8 in the SOIC8 package are no-connect (N/C) terminals - they are not bonded to the die and must remain unconnected on the PCB. Routing traces or placing vias on these pads violates the absolute maximum ratings and may cause latch-up or premature failure.

Can MP156GS-Z be used in a Buck converter without an optocoupler?

Yes - MP156GS-Z is specifically designed for primary-side regulation in Buck topology. It samples output voltage indirectly via a capacitor divider network referenced to SOURCE, eliminating the need for optocoupler, secondary-side shunt regulator, or auxiliary winding.

What protection features are integrated, and how do they reset?

MP156GS-Z integrates thermal shutdown (TSD), VCC UVLO, overload protection (OLP), short-circuit protection (SCP), and open-loop detection. All protections trigger auto-restart: after fault removal, VCC discharges to 2.4V, then the internal HV current source recharges it to 5.3V to resume switching - typical restart time is 1–3 seconds depending on VCC capacitor value.

What is the minimum off-time, and why is it critical for stability?

The minimum off-time is 18µs under normal operation (soft-starting from 72µs). It prevents sub-harmonic oscillation in CCM mode, enforces safe demagnetization in Flyback, and sets the upper limit for output power - undersized inductors violating this constraint cause regulation loss and thermal stress at full load.