Monolithic Power Systems Inc. MP172GJ-Z

Overview

MP172GJ-Z from Monolithic Power Systems is a 700 V primary-side constant-voltage (CV) regulator with integrated MOSFET, supporting buck/boost/buck-boost/flyback topologies in non-isolated off-line power supplies. It delivers up to 120 mA output current in CCM, achieves <30 mW no-load consumption, and operates across -40°C to +125°C junction temperature for home appliance standby power.

For engineers reviewing the MP172GJ-Z datasheet, MP172GJ-Z pinout, MP172GJ-Z application, or MP172GJ-Z equivalent, this device requires attention to its green-mode frequency foldback, peak-current compression, VCC UVLO thresholds (5.1–5.8 V), and thermal shutdown at 150°C - all critical for low-power AC/DC converter design and reliability validation.

Technical Context

The MP172GJ-Z implements primary-side CV regulation without optocoupler feedback by sampling output voltage via a capacitor (C3) during freewheeling diode conduction. Its internal error amplifier compares FB voltage to a 2.55 V reference and adjusts switching via peak-current limiting and minimum-off-time control.

It uses green-mode operation: switching frequency and peak current both scale down under light load, reducing no-load power to <30 mW. Protection includes auto-restart OLP (175 ms delay), SCP (330–510 mA threshold), TSD (150°C trip, 30°C hysteresis), and open-loop detection (<0.5 V FB).

Key Specifications

Pinout & Package

MP172GJ-Z is housed in a TSOT23-5 package (2.9 × 1.6 × 0.85 mm), optimized for compact non-isolated AC/DC converters. The exposed pad is not electrically connected but aids thermal dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP172GJ-Z, MP172A-GJ-Z offers documented improvements in OLP consistency and reference accuracy for new designs, while MP174GQ-Z provides higher voltage ruggedness and integrated soft-start - making it preferable for industrial-grade surge resilience without changing layout.

Availability

MP172GJ-Z is available at Aetrix Electronics and suitable for home appliance standby supplies, industrial sensor node power, LED driver bias rails, and white goods control board power requiring stable component supply and long-term sourcing continuity.

Supply support for MP172GJ-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.

The MP172 product line targets cost-sensitive, low-power AC/DC conversion in consumer and industrial equipment, emphasizing primary-side regulation, integrated HV MOSFETs, and green-mode efficiency for regulatory compliance.

FAQ

What is the recommended minimum off-time for MP172GJ-Z in CCM operation?

The minimum off-time is 7.5–12.5 μs (typ 10 μs), which directly limits maximum output power in continuous conduction mode. This parameter governs energy transfer per cycle and must be respected in inductor selection to avoid saturation and ensure regulation stability across line and load variations.

Can MP172GJ-Z be used in flyback topology with primary-side regulation?

Yes - MP172GJ-Z supports flyback configuration with indirect feedback via a sampling capacitor on the secondary side. The FB pin senses reflected voltage during demagnetization, enabling isolation without optocoupler. Layout must minimize parasitic coupling to maintain regulation accuracy within ±5%.

Why does MP172GJ-Z specify "NOT RECOMMENDED FOR NEW DESIGNS"?

This designation reflects MPS's release of the improved MP172A variant with tighter FB reference tolerance, faster OLP response, and reduced start-up current. MP172GJ-Z remains fully functional and supported for legacy designs and existing production, but MP172A-GJ-Z is preferred for new schematics.

How is VCC supplied during startup and normal operation?

VCC is self-supplied from the DRAIN pin via an internal high-voltage regulator. At startup, the regulator charges the external VCC capacitor until reaching 5.7 V (VCCOFF); then it turns off. During operation, VCC is maintained by energy transferred from the transformer or inductor during flyback/buck-boost cycles.

What is the purpose of the leading-edge blanking (LEB) feature?

LEB disables the current-sense comparator for 350 ns after MOSFET turn-on to ignore turn-on spikes caused by parasitic capacitance and diode reverse recovery. This prevents false overcurrent triggering and ensures reliable switching in noisy high-dv/dt environments like AC/DC front-ends.

Does MP172GJ-Z require a dummy load for stable regulation?

Yes - a minimum 3 mA dummy load is recommended to ensure sufficient inductor energy for sampling capacitor (C3) charging, especially at light loads. Without it, regulation degrades due to insufficient FB voltage sampling, causing output drift or instability in standby conditions.

How does frequency foldback improve efficiency at light load?

Frequency foldback reduces switching losses by lowering fs as load decreases - e.g., from 36 kHz at full load to ~5 kHz at 10% load. Combined with peak-current compression, this cuts total power loss, enabling <30 mW no-load consumption while maintaining regulation accuracy.