Monolithic Power Systems Inc. MP174GS

Overview

MP174GS from Monolithic Power Systems is a 700V primary-side constant-voltage (CV) off-line regulator with integrated MOSFET, supporting Buck, Buck-Boost, Boost, and Flyback topologies. It delivers up to 400mA output current in CCM mode, achieves <30mW no-load power consumption, and features green-mode operation with frequency foldback and peak-current compression for high light-load efficiency. It targets non-isolated low-power AC/DC conversion in home appliances and standby power supplies.

For engineers reviewing the MP174GS datasheet, MP174GS pinout, MP174GS application, or MP174GS equivalent, key selection criteria include its 700V/13.5Ω integrated MOSFET, 2.55V FB reference voltage, 12–15μs minimum off-time, thermal shutdown at 150°C, and SOIC-8 package compatibility with standard PCB layout practices for EMI-sensitive offline regulators.

Technical Context

The MP174GS implements primary-side regulation using internal error amplifier sampling of the FB pin 6μs after MOSFET turn-off, referenced to a 2.55V precision bandgap. Its green-mode control dynamically reduces both switching frequency and peak current limit (660mA → ~200mA) as load decreases, enabling sub-30mW no-load consumption.

Protection logic includes auto-restart OLP triggered by FB <1.7V for ≥220ms, SCP via 900mA threshold with 180ns leading-edge blanking, OTP at 150°C with 30°C hysteresis, and open-loop detection at FB <0.5V. VCC management uses internal HV startup from DRAIN, with UVLO (5.3V ON / 5.6V OFF) and latch-off discharge at 3.4V.

Key Specifications

Pinout & Package

MP174GS is housed in an SOIC-8 package with exposed thermal pad (pin 5 connected to SOURCE). The package supports standard reflow profiles and provides 96°C/W junction-to-ambient thermal resistance on 4-layer PCBs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP173GS, MP174GS adds 50V headroom and green-mode operation for better surge resilience and standby efficiency; versus LNK3206G, it eliminates optocoupler dependency and reduces component count by 4–6 parts, though forfeits reinforced isolation.

Availability

MP174GS is available at Aetrix Electronics and suitable for smart home appliance power, industrial sensor node supply, and white goods control board applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MP174GS 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 manufacturing partners worldwide.

The MP174 product line delivers highly integrated primary-side regulators targeting cost-sensitive, non-isolated offline power conversion in consumer and industrial equipment - emphasizing minimal external components, ultra-low standby power, and robust protection.

FAQ

What topologies does MP174GS support, and which require isolation?

MP174GS supports Buck, Buck-Boost, Boost, and Flyback topologies. Only Flyback provides galvanic isolation; Buck, Buck-Boost, and Boost are non-isolated and require careful safety spacing on PCB. The IC's 700V MOSFET enables direct connection to rectified AC line in all configurations.

How does MP174GS achieve <30mW no-load power consumption?

It combines three techniques: frequency foldback (reducing switching frequency under light load), peak-current compression (lowering ILIMIT from 660mA toward 200mA), and low ICC (720μA typical active current). These reduce dynamic and static losses simultaneously, verified at 265VAC input with 12V/0mA output.

What is the role of the N/C pins (5, 6, 8) in SOIC-8 package?

Pins 5, 6, and 8 are internally unconnected. Per MPS layout guidelines, they may be left floating or tied to SOURCE (pins 3–4) to improve thermal conduction and EMI performance. They must never be connected to VCC, FB, or high-voltage traces.

Can MP174GS operate without an external VCC capacitor?

No. An external 1–10μF capacitor is mandatory between VCC (pin 1) and SOURCE (pins 3–4). It sustains control circuitry during MOSFET on-time and stabilizes the internal regulator. Omitting it causes erratic startup, UVLO cycling, or immediate thermal shutdown.

What is the minimum recommended inductor value for a 12V/300mA Buck design?

For reliable CCM operation at full load, MPS recommends ≥0.36mH (per Figure 7). However, to maintain switching frequency above 20kHz and avoid excessive core loss, a 1.2mH inductor is used in the reference design (Figure 10) - balancing efficiency, size, and ripple.

How does open-loop protection trigger, and what happens afterward?

Open-loop protection activates when FB voltage drops below 0.5V for >100ms, indicating broken feedback path or failed output capacitor. The IC stops switching, discharges VCC to 2.4V via 16μA current source, then restarts after VCC recharges to 5.6V - ensuring safe recovery without manual reset.

Is MP174GS compliant with RoHS and halogen-free standards?

Yes. MP174GS is lead-free, halogen-free, and fully compliant with EU RoHS Directive 2011/65/EU. MPS confirms green status on its Quality Assurance webpage, and the device carries the "MPS Green" designation in official documentation.