Monolithic Power Systems Inc. MP158GJ-P

Overview

MP158GJ-P from Monolithic Power Systems is a primary-side, off-line switching regulator IC with integrated 500V MOSFET, delivering constant voltage regulation without opto-coupler in Buck, Buck-Boost, Boost, and Flyback topologies. It achieves <30mW no-load power consumption, supports up to 2W output power, and operates across –40°C to +125°C junction temperature for home appliance standby and low-power industrial control applications.

For engineers reviewing the MP158GJ-P datasheet, MP158GJ-P pinout, MP158GJ-P application, or MP158GJ-P equivalent, this device is selected for green-mode flyback/Buck designs requiring high light-load efficiency, internal thermal shutdown with auto-restart, and VCC UVLO with 250mV hysteresis - all in a space-constrained TSOT23-5 package.

Technical Context

The MP158GJ-P implements primary-side constant voltage (CV) regulation using feedback sampling via an external capacitor, eliminating opto-coupler dependency. Its green-mode operation dynamically reduces both peak current (down to ~16mA at no load) and switching frequency under decreasing load, enabling sub-30mW no-load consumption.

Protection logic integrates timer-based overload protection (120ms delay), short-circuit detection (220mA threshold), open-loop detection (<60mV FB), and thermal shutdown (150°C trip with 30°C hysteresis). The internal 500V MOSFET and self-biased VCC supply enable single-stage AC/DC conversion with minimal external components.

Key Specifications

Pinout & Package

MP158GJ-P is housed in a 5-pin TSOT23-5 package with exposed drain pad for thermal enhancement. Pin 1 = VCC (control supply), Pin 2 = FB (voltage feedback input), Pins 3 & 4 = SOURCE (MOSFET source and ground reference), Pin 5 = DRAIN (integrated 500V MOSFET drain and HV current source input).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP158GJ-P, MP157GJ-Z trades output capability and topology flexibility for marginally lower cost in non-isolated apps, while LNK3206G adds safety features and EMI robustness at the expense of green-mode efficiency and package size.

Availability

MP158GJ-P is available at Aetrix Electronics and suitable for home appliance standby power, industrial control auxiliary supplies, and IoT edge node power management requiring stable component supply across multi-year production cycles.

Supply support for MP158GJ-P 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, headquartered in Kirkland, WA, with global design and support centers.

The MP158 product line delivers highly integrated, energy-efficient primary-side regulators targeting cost-sensitive, space-constrained off-line power conversion in consumer and industrial applications.

FAQ

What topologies does MP158GJ-P support, and which require external components?

MP158GJ-P supports Buck, Buck-Boost, Boost, and Flyback topologies. Buck and Boost require no isolation; Flyback requires a transformer with auxiliary winding for feedback sampling. All configurations use the same IC but differ in external passive selection - no additional ICs or opto-couplers are needed in any case.

How does MP158GJ-P achieve <30mW no-load power consumption?

It combines three mechanisms: frequency foldback (reducing switching frequency below 10kHz), peak-current compression (lowering ILimit from 101mA to ~16mA), and ultra-low ICC (165μA static current, 16μA latch-off phase). These are coordinated by internal green-mode logic that scales both timing and current thresholds with load.

Can MP158GJ-P operate without an external VCC capacitor?

No. An external VCC capacitor (typically 1–4.7μF ceramic) is mandatory. It stores energy during MOSFET off-time to sustain internal circuitry between cycles. The IC uses internal high-voltage startup current from the DRAIN pin to charge this capacitor initially, then switches to internal regulation once VCC reaches 5.6V.

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

The FB pin senses voltage across an external RC network connected to the output. A 2.55V internal reference compares against the sampled FB voltage. Output voltage is set by R1/R2 divider per Vo = 2.55V × (1 + R1/R2); R2 is typically 5–10kΩ to balance noise immunity and leakage error.

Does MP158GJ-P include built-in EMI reduction features?

Yes. It incorporates leading-edge blanking (350ns on DRAIN, 180ns for SCP), exponential ramp compensation synchronized to load, and frequency jitter inherent to green-mode operation - all reducing conducted and radiated emissions without external filters.

How does thermal shutdown behave during continuous overload?

At 150°C junction temperature, MP158GJ-P shuts down and discharges the VCC capacitor via a 16μA current source. Once VCC falls to 2.4V, the internal HV regulator re-engages and recharges VCC. Operation resumes only after junction cools to 120°C - providing safe, self-resetting protection without external intervention.