Monolithic Power Systems Inc. MP175LGS-Z

Overview

MP175LGS-Z from Monolithic Power Systems is a 700V non-isolated offline primary-side constant-voltage (CV) regulator with integrated 700V/4.5Ω MOSFET, supporting buck/buck-boost/boost/flyback topologies, delivering up to 600mA output current and featuring brown-in protection - deployed in low-power home appliance standby supplies.

For engineers reviewing the MP175LGS-Z datasheet, MP175LGS-Z pinout, MP175LGS-Z application, or MP175LGS-Z equivalent, key selection criteria include its SOIC-8 package, 700V drain rating, <30mW no-load consumption, green-mode frequency foldback, and primary-side CV regulation without optocoupler.

Technical Context

The MP175LGS-Z implements primary-side CV control using feedback voltage (VFB = 2.43V typ) sampled at the FB pin to regulate output voltage without secondary-side sensing. Its internal high-voltage current source powers VCC directly from DRAIN, enabling operation with a sub-μF VCC capacitor.

It employs adaptive green-mode operation: switching frequency (fSW) and peak current limit (ILIMIT = 1.1A typ) both scale downward under light load to maintain efficiency. Protection logic includes brown-in detection (VDS_BI = 40V), open-loop detection (VOLD = 0.3V), and 4096-cycle OLP counter for robust fault recovery.

Key Specifications

Pinout & Package

MP175LGS-Z is housed in an SOIC-8 package with exposed DRAIN pads (pins 5–8) for thermal conduction and high-voltage isolation. The package complies with JEDEC MS-012 AA, features 1.27mm pitch, and supports standard reflow profiles (lead-free, RoHS-compliant).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP175LGS-Z, MP174GSO-Z sacrifices universal input capability and brown-in protection for lower unit cost, while LNK3206D requires additional external components and delivers inferior light-load efficiency - making MP175LGS-Z the optimal choice for new designs targeting <30mW standby and robust brownout recovery.

Availability

MP175LGS-Z is available at Aetrix Electronics and suitable for home appliance standby supplies, white goods control logic, and industrial sensor node power requiring stable component supply, long-term lifecycle support, and RoHS-compliant sourcing.

Supply support for MP175LGS-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 power management ICs, with over two decades of expertise in integrated DC/DC conversion and AC/DC regulation.

The MP175L product line targets cost-sensitive, low-power offline applications demanding high integration, ultra-low standby consumption, and simplified board-level design - specifically for consumer and industrial mains-powered devices.

FAQ

What is the minimum recommended VCC capacitor value for MP175LGS-Z?

The MP175LGS-Z supports a VCC capacitor as low as 0.47μF due to its integrated high-voltage current source. A 1μF/25V ceramic or electrolytic capacitor is recommended to ensure reliable start-up across temperature and line variations while minimizing board space.

Can MP175LGS-Z operate in flyback topology without an optocoupler?

Yes - MP175LGS-Z uses primary-side constant-voltage regulation with internal compensation and FB sampling to achieve ±5% output accuracy in flyback configurations. It eliminates the need for optocoupler, TL431, and auxiliary winding, verified in MPS Application Note AN-137.

How does brown-in protection differ from standard UVLO in MP175LGS-Z?

Brown-in protection monitors DRAIN voltage (VDS) to prevent restart until it exceeds 40V after shutdown, whereas UVLO (VCCL = 7.9V) disables switching when VCC drops too low. Brown-in avoids repeated cycling during marginal input recovery - a distinct behavior confirmed in the Functional Block Diagram and Operation section.

What is the maximum achievable output power with MP175LGS-Z in buck topology?

In continuous conduction mode (CCM) with optimized magnetics and layout, MP175LGS-Z delivers up to 9W output power (e.g., 5V/1.8A or 12V/750mA), limited by thermal dissipation in SOIC-8 and peak current limit (ILIMIT = 1.1A). Derating is required above 75°C ambient.

Does MP175LGS-Z require an external freewheeling diode in buck configuration?

Yes - MP175LGS-Z integrates only the high-side MOSFET; an external ultra-fast recovery diode (e.g., STTH2R06) is required for the freewheeling path. Diode selection must account for peak inverse voltage ≥700V and average current ≥600mA, per the Application Information section.

Is open-loop detection (OLD) active during soft-start?

No - OLD is blanked during the 8-step soft-start sequence (total ~1.2ms), as explicitly stated in the Soft Start section. This prevents false triggering during initial ramp-up when FB voltage is settling. OLD resumes normal operation once soft-start completes.

What PCB layout practices are critical for EMI performance with MP175LGS-Z?

Minimize the high-di/dt loop formed by DRAIN–inductor–diode–output capacitor; place a 1nF ceramic capacitor between FB and GND adjacent to the IC; use large copper pour on DRAIN pins for thermal relief; and separate GNDA and GNDP with single-point connection near GNDP pin - all validated in the PCB Layout Guidelines (page 15).