Monolithic Power Systems Inc. HF920GS-Z

Overview

HF920GS-Z from Monolithic Power Systems is a monolithic 900V flyback switching regulator IC with integrated MOSFET (R_DS(ON) = 15 Ω @ 25°C), fixed-frequency peak-current-mode control, programmable switching frequency up to 150 kHz, and ultra-low standby power (<30 mW no-load consumption). It targets high-reliability AC/DC power supplies in smart meters, industrial controls, and large appliances operating on poor or wide-range AC grids (85–420 V_AC).

For engineers reviewing the HF920GS-Z datasheet, HF920GS-Z pinout, HF920GS-Z application, or HF920GS-Z equivalent, key selection criteria include its 900V drain rating, burst-mode light-load efficiency, frequency jittering for EMI reduction, OTP co-integrated with the power MOSFET, and PRO pin hysteresis for external fault handling.

Technical Context

The HF920GS-Z implements peak-current-mode control with internal slope compensation and leading-edge blanking (t_LEB1 = 385 ns, t_LEB2 = 350 ns) to ensure stable operation under transient load and transformer leakage conditions. Its feedback loop uses FB voltage (0.4–0.8 V burst thresholds) to regulate output via optical coupling while simultaneously managing OLP (8192-cycle counter), SCP (V_SCP = 1.5 V), and OVP (V_OVP = 25.5 V, 70 μs delay).

Switching frequency is resistor-programmable (e.g., 49 kHz at R_FSET = 200 kΩ) with ±3.5% jittering and optional frequency-doubling mode triggered at V_FB ≥ 3.65 V - enabling robust operation despite up to 50% inductance drop from magnetic interference. Start-up is enabled by a 900V drain current source (I_Charge = 2 mA @ 400 V), and VCC management includes UVLO hysteresis (V_CCH = 13 V / V_CCL = 9 V).

Key Specifications

Pinout & Package

HF920GS-Z is packaged in SOIC14-11, a 14-pin surface-mount package with exposed thermal pad (GND-connected pins 1, 2, 7, 8), NC pin (13), and optimized thermal resistance (θ_JA = 70°C/W, θ_JC = 35°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP101GZ and UCC28631DR, HF920GS-Z uniquely combines 900V integration, on-die OTP, frequency doubling, and sub-30 mW standby - making it the only solution qualified for high-voltage, ultra-low-power, magnetically noisy environments like utility-grade metering and factory automation.

Availability

HF920GS-Z is available at Aetrix Electronics and suitable for smart metering, industrial PLC power supplies, and large-appliance AC/DC conversion requiring stable component supply across extended product lifecycles and global regulatory certifications.

Supply support for HF920GS-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 over two decades of leadership in monolithic high-voltage integration and energy-efficient power conversion.

The HF920 belongs to MPS's high-voltage offline regulator product line, engineered specifically for reliability-critical AC/DC applications in utility infrastructure, industrial control, and home appliance markets where wide-input-range operation and ultra-low standby power are mandatory.

FAQ

What is the maximum continuous output power achievable with HF920GS-Z at 230 V_AC ±15%?

The HF920GS-Z delivers up to 10 W in SOIC14-11 package under 230 V_AC ±15% input, as validated per Table 1 in the datasheet. This assumes TA = 50°C, 12.5 V output, BCM operation at minimum input, and GND connected to 2.5 cm² copper area. Derating is required above 50°C ambient or with reduced PCB copper.

How does the frequency-doubling mode improve robustness against magnetic interference?

When external magnetic fields reduce transformer inductance by up to 50%, the HF920GS-Z doubles its switching frequency (e.g., from 50 kHz to 100 kHz) upon detecting V_FB ≥ 3.65 V. This maintains constant peak current and prevents saturation-induced overcurrent, ensuring uninterrupted regulation without output collapse.

Can HF920GS-Z operate without an auxiliary winding for VCC supply?

No - the internal high-voltage current source on the D pin only provides start-up energy. Once VCC reaches VCCH (13 V), the IC switches to auxiliary-winding-derived supply. Continuous operation without auxiliary winding will cause VCC undervoltage lockout and shutdown after initial start-up.

What is the purpose of the PRO pin, and how should it be implemented externally?

The PRO pin provides hysteresis-enabled external shutdown (V_PRO = 3.1 V ±0.1 V, 0.2 V hysteresis). It is commonly used for input overvoltage protection via a resistor divider from the bulk DC bus, or for remote thermal sensing using an NTC thermistor network - triggering auto-restart once fault clears.

Does HF920GS-Z require external slope compensation?

No - slope compensation is fully integrated and automatically scaled with programmed switching frequency (e.g., 21 mV/μs at R_FSET = 200 kΩ). This eliminates external components and ensures stable current-mode control across all operating conditions without tuning.

How is the burst-mode threshold set, and what happens during burst operation?

Burst mode activates when FB voltage falls below V_BURL = 0.5 V and deactivates when it rises above V_BURH = 0.7 V. During burst, the IC stops switching entirely until output droop raises FB back above V_BURH, then resumes full-frequency operation - minimizing switching losses at light loads.

What thermal derating applies to the SOIC14-11 package at 70°C ambient?

At T_A = 70°C, maximum continuous power dissipation drops to 0.95 W (calculated as (150°C − 70°C) / 70°C/W). To sustain 10 W output, forced airflow or enhanced copper pour beyond the 2.5 cm² minimum is required to maintain junction temperature ≤125°C.