Monolithic Power Systems Inc. HF920AGS-Z

Overview

HF920AGS-Z from Monolithic Power Systems is a 900V monolithic flyback switching regulator IC integrating a high-voltage power MOSFET, peak-current-mode controller, and comprehensive protection circuitry. It delivers up to 10W output at 230Vac±15%, operates with programmable fixed frequency up to 150kHz, achieves <30mW no-load consumption, and features integrated OTP on the same die as the 900V MOSFET - designed for smart metering, industrial controls, and appliances operating on unstable AC grids.

For engineers reviewing the HF920AGS-Z datasheet, HF920AGS-Z pinout, HF920AGS-Z application, or HF920AGS-Z equivalent, key selection criteria include its 900V/15Ω integrated MOSFET, PRO-pin programmable UVP/OVP thresholds (0.25V/3.1V), burst-mode light-load efficiency, ±3.5% frequency jittering for EMI reduction, and SOIC14-11 thermal performance (θJA = 70°C/W).

Technical Context

The HF920AGS-Z implements peak-current-mode control with internal slope compensation and leading-edge blanking (tLEB1 = 385ns, tLEB2 = 350ns), enabling stable operation in CCM/BCM across wide input ranges (85–420Vac). Its feedback loop uses FB pin voltage division (Kdiv = 3.7) to set primary current limit (VCSL = 0.97V typ), while burst mode activates below VBURL = 0.5V and exits above VBURH = 0.7V.

Protection architecture includes time-based overload detection (8192-cycle counter), short-circuit shutdown at VSCP = 1.5V, VCC OVP at 25.2V with 70μs delay, and thermal shutdown at 150°C with 30°C hysteresis. Frequency is set externally via FSET resistor (VFSET = 1.25V), and PRO pin supports external UVP/OVP with 0.2V hysteresis and 20μs response.

Key Specifications

Pinout & Package

HF920AGS-Z is housed in a SOIC14-11 package with exposed thermal pad (GND-connected), offering θJA = 70°C/W and θJC = 35°C/W for high-power density offline designs.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar offline flyback regulator applications.

Compared with MP174G and UCC28881DR, HF920AGS-Z uniquely combines 900V rating, PRO-pin programmability, and ±3.5% jittering - making it the only option qualified for 420Vac smart meter front-end power with certified EMI performance and grid-failure response.

Availability

HF920AGS-Z is available at Aetrix Electronics and suitable for smart metering, industrial PLC power supplies, and large appliance control systems requiring stable component supply across extended product lifecycles and fluctuating AC grid conditions.

Supply support for HF920AGS-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 core expertise in integrated power stages and advanced control architectures.

The HF920A product line targets high-reliability offline AC/DC conversion in harsh grid environments - specifically engineered for metering, industrial control, and appliance applications demanding 900V tolerance, ultra-low standby power, and robust fault handling.

FAQ

What is the maximum continuous output power achievable with HF920AGS-Z at 230Vac±15%?

The HF920AGS-Z delivers up to 10W continuous output power under 230Vac±15% input conditions when mounted on a SOIC14-11 test board with 2.5cm² GND copper area and operated at TA = 50°C. This rating assumes single-output configuration (12.5V), BCM operation at minimum input, and proper transformer turns ratio (N = 5) to limit VDS stress.

How does the PRO pin implement input under-voltage protection?

The PRO pin triggers shutdown when pulled below 0.25V (typical) with 0.2V hysteresis. In a typical implementation, a resistive divider from rectified DC bus to PRO sets the trip point - e.g., 54VDC input causes PRO to fall to 0.25V, initiating immediate shutdown. Recovery occurs when input rises to 59VDC, lifting PRO above 0.25V + 0.2V hysteresis.

Can HF920AGS-Z operate in continuous conduction mode (CCM) across the full input range?

Yes - the integrated slope compensation and peak-current-mode control enable stable CCM operation even at duty cycles exceeding 50%. Designers achieve this by selecting primary inductance to maintain KP (ripple-to-peak ratio) between 0.8–1.0 at minimum input (85Vac), ensuring no subharmonic oscillation without external compensation.

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

HF920AGS-Z employs dual LEB: tLEB1 = 385ns blocks current-sense comparator during MOSFET turn-on to ignore switching spikes, while tLEB2 = 350ns disables short-circuit protection comparator separately. This prevents false SCP triggering during normal turn-on while maintaining fast fault response for true short events.

How does frequency jittering reduce EMI in PLC-sensitive applications?

Frequency jittering spreads the fundamental switching energy across a ±3.5% bandwidth (e.g., 49kHz ±1.7kHz) using a 256-cycle carrier. This reduces peak spectral amplitude by ~10dB compared to fixed-frequency operation, allowing simpler, lower-cost EMI filters that meet EN 55022 Class B limits without compromising PLC signal integrity in 3–500kHz bands.

Is the SOIC14-11 package thermally enhanced compared to SOIC8-7A?

Yes - the SOIC14-11 package offers θJA = 70°C/W versus 96°C/W for SOIC8-7A, delivering 27% better thermal resistance. Its larger GND pad area (2.5cm² vs. 3cm² for SOIC8-7A) and additional thermal vias enable 10W output capability at 230Vac, whereas SOIC8-7A is limited to 9.5W under identical conditions.