Monolithic Power Systems Inc. MP157GJ-P

Overview

MP157GJ-P from Monolithic Power Systems is a primary-side constant-voltage (CV) off-line regulator 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 MP157GJ-P datasheet, MP157GJ-P pinout, MP157GJ-P application, or MP157GJ-P equivalent, key selection criteria include its TSOT23-5 package footprint, primary-side regulation eliminating optocoupler dependency, VCC UVLO hysteresis (230mV), FB threshold (2.55V), and thermal shutdown at 150°C - all critical for compact, cost-sensitive, energy-compliant offline SMPS designs.

Technical Context

The MP157GJ-P implements primary-side CV control using feedback sampled via an internal capacitor-based hold circuit, enabling accurate output regulation without secondary-side sensing. Its green-mode operation dynamically scales switching frequency and peak current with load - reducing both conduction and switching losses at light loads.

It integrates a 500V vertical DMOS power switch with 10Ω R_DS(on), internal 400ns leading-edge blanking, and a self-powered start-up circuit drawing 3.5mA typical from the DRAIN pin. Protection includes timer-based OLP (150ms delay), SCP (900mA trigger), open-loop detection (<60mV FB), and auto-restart thermal shutdown.

Key Specifications

Pinout & Package

MP157GJ-P is housed in a thermally enhanced TSOT23-5 package with exposed drain pad for improved heat dissipation. The 5-pin configuration supports minimal external component count and board space savings in ultra-compact offline regulators.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP157GJ-P, MP158GJ-Z offers headroom for future power scaling without layout change, while LNK304DG trades integration and efficiency for legacy compatibility and tighter CV spec - making MP157GJ-P optimal for new cost- and size-constrained 6W designs.

Availability

MP157GJ-P is available at Aetrix Electronics and suitable for home appliance standby supplies, industrial sensor node power, and white goods control board applications requiring stable component supply, RoHS-compliant packaging, and long-term lifecycle support.

Supply support for MP157GJ-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, with design centers in the US, China, and Taiwan, and global distribution through authorized partners.

The MP157 product line delivers highly integrated, energy-efficient primary-side regulators targeting cost-sensitive, space-constrained offline AC/DC conversion in consumer and industrial equipment - emphasizing simplicity, reliability, and regulatory compliance.

FAQ

What topologies does MP157GJ-P support, and which require isolation?

MP157GJ-P supports Buck, Buck-Boost, Boost, and Flyback topologies. Only Flyback provides galvanic isolation between input and output; the others are non-isolated and require careful attention to safety spacing and grounding per IEC 62368-1. Flyback is recommended for applications needing reinforced insulation or user-accessible outputs.

How is output voltage set without a secondary-side feedback loop?

MP157GJ-P uses primary-side regulation: the FB pin samples voltage across a capacitor coupled to the output via a resistive divider and transformer auxiliary winding. An internal sample-and-hold circuit captures peak output voltage during freewheeling, enabling direct CV control with ±5% typical accuracy - no optocoupler or TL431 required.

What is the minimum off-time limitation, and why does it matter?

The MP157GJ-P enforces a 13.1μs minimum off-time during normal operation (52.4μs at startup). This limits maximum switching frequency and ensures sufficient time for inductor demagnetization and FB sampling. It directly constrains maximum output power - undersized inductors may fail to deliver full load due to duty-cycle saturation.

Can MP157GJ-P operate without an auxiliary VCC winding?

Yes - the internal HV start-up circuit draws current directly from the DRAIN pin to charge the VCC capacitor. Once VCC reaches 4.6V, the HV source disables and the IC runs from VCC. A 4.7μF ceramic capacitor suffices for hold-up; no auxiliary winding is needed unless VOUT exceeds 7V, where clamping improves efficiency.

What protection features activate during short-circuit conditions?

Under short-circuit, MP157GJ-P triggers Short Circuit Protection (SCP) when sensed peak current exceeds 900mA, halting switching immediately. Concurrently, VCC discharges via a 16μA internal current source until it falls below 2.35V, then restarts after VCC recharges to 4.45V - implementing hiccup-mode recovery to limit average power dissipation and prevent thermal runaway.

Is MP157GJ-P compliant with modern energy efficiency standards?

Yes - with <100mW no-load power consumption and green-mode operation that maintains >65% efficiency at 10% load, MP157GJ-P meets DOE Level VI, EU CoC Tier 2, and Energy Star 2.0 standby requirements for sub-6W AC/DC converters without additional circuitry.

How does the thermal shutdown behave, and is it auto-recovering?

MP157GJ-P enters thermal shutdown at 150°C junction temperature and stops switching. The internal HV current source then discharges VCC to ~2.4V before restarting the charge cycle. This auto-restart behavior continues until ambient conditions allow junction temperature to fall below the hysteresis threshold - preventing latch-up while protecting against sustained overheating.