Monolithic Power Systems Inc. MP172GJ-P

Overview

MP172GJ-P from Monolithic Power Systems is a 700 V primary-side constant-voltage (CV) regulator with integrated MOSFET, supporting buck/boost/buck-boost/flyback topologies for 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. It is used in standby power and home appliance auxiliary supplies.

For engineers reviewing the MP172GJ-P datasheet, MP172GJ-P pinout, MP172GJ-P application, or MP172GJ-P equivalent, this page provides verified technical context, validated pin functions, topology-specific design meaning, and real-world protection behavior - all derived from Monolithic Power's official MP172 Rev. 1.01 documentation.

Technical Context

The MP172GJ-P implements green-mode operation via simultaneous frequency foldback and peak-current compression: switching frequency drops below 36 kHz and peak current limit decreases from 210 mA as load declines, enabling <30 mW no-load power. Its internal error amplifier samples FB 6 µs after MOSFET turn-off against a 2.55 V reference to regulate output voltage without optocoupler feedback.

Protection logic includes auto-restart OLP (175 ms delay at 36 kHz), SCP (400 mA threshold with 180 ns blanking), thermal shutdown at 150°C (30°C hysteresis), and open-loop detection triggered when FB falls below 0.5 V. Startup relies on internal high-voltage regulator sourcing from DRAIN, with VCCON = 5.5 V and VCCOFF = 5.7 V.

Key Specifications

Pinout & Package

MP172GJ-P is housed in a TSOT23-5 package with exposed drain pad for thermal enhancement. Pin 1 is VCC, Pin 2 is FB, Pins 3 and 4 are SOURCE (common ground reference for VCC and FB), and Pin 5 is DRAIN (700 V MOSFET drain and HV current source input). Pins marked NC are not internally connected.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP172GJ-P, MP172A-GJ-Z offers verified long-term stability and tighter regulation tolerances for production-critical designs, while MP173GS-P extends power delivery headroom without changing board layout - making both viable depending on whether lifecycle assurance or output scalability is prioritized.

Availability

MP172GJ-P is available at Aetrix Electronics and suitable for home appliance standby supplies, white goods auxiliary power, and industrial control panel logic requiring stable component supply and RoHS-compliant packaging.

Supply support for MP172GJ-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 core expertise in DC/DC conversion, LED drivers, and motor control.

The MP172 product line targets cost-sensitive, non-isolated off-line power conversion in consumer and industrial applications, emphasizing integration, green-mode efficiency, and simplified system-level design.

FAQ

What topology options does MP172GJ-P support, and which require isolation?

MP172GJ-P supports buck, boost, buck-boost, and flyback topologies. Only flyback provides galvanic isolation; the other three are non-isolated. In flyback, feedback is indirect via a sampling capacitor on the secondary side, whereas buck/boost/buck-boost use direct primary-side sensing. Isolation requires transformer coupling and careful creepage/clearance layout per safety standards.

Why is MP172GJ-P labeled "NOT RECOMMENDED FOR NEW DESIGNS"?

This designation reflects Monolithic Power's formal obsolescence notice: MP172GJ-P has been superseded by MP172A-GJ-Z, which features tighter parameter tolerances, improved protection timing accuracy, and enhanced ESD robustness. While MP172GJ-P remains functional and in stock, MPS no longer qualifies it for new product introductions or long-term production commitments.

How does MP172GJ-P achieve <30 mW no-load consumption?

It combines three mechanisms: (1) frequency foldback - switching frequency drops below 10 kHz at no load; (2) peak-current compression - current limit scales down from 210 mA to ~50 mA; and (3) ultra-low ICC of 200 µA in quiescent state. These reduce dynamic and static losses simultaneously, meeting stringent global no-load regulations without external dummy loads.

What is the role of the sampling capacitor (C3) in MP172GJ-P feedback?

C3 holds the output voltage during MOSFET off-time and feeds it to the FB pin. Its value (typically 22 nF) balances regulation accuracy and transient response: too small causes poor light-load regulation; too large slows feedback loop dynamics and risks instability. The capacitor charges through the freewheeling diode and discharges into the FB network, enabling true primary-side CV sensing.

Can MP172GJ-P operate without an external VCC capacitor?

No. An external VCC capacitor (typically 1–4.7 µF) is mandatory. It stores energy supplied by the internal HV regulator during MOSFET on-time and powers the control circuitry during off-time. Without it, VCC collapses below VCCON, causing repeated start-stop cycling and preventing stable regulation. The capacitor also filters switching noise coupled into the VCC rail.

What are the critical PCB layout guidelines for MP172GJ-P in TSOT23-5?

Minimize the high-di/dt loop formed by DRAIN–SOURCE–inductor–diode; place the FB-to-SOURCE capacitor (470 pF) directly adjacent to pins 2 and 3; connect the exposed DRAIN pad to a large copper pour for thermal relief; keep feedback traces short and away from noisy nodes; and avoid routing VCC or FB near DRAIN or switching inductors to prevent coupling-induced regulation errors.