Monolithic Power Systems Inc. HF920GSE-Z

Overview

HF920GSE-Z from Monolithic Power Systems is a monolithic 900V flyback switching regulator IC with integrated MOSFET, designed for offline AC/DC power supplies in smart meters, industrial controls, and large appliances operating on poor AC grids. It delivers up to 9.5W at 230Vac±15% (SOIC14-11), features programmable fixed-frequency operation up to 150kHz, burst-mode standby consumption <30mW, and integrated OTP, OVP, OLP, SCP, and UVLO.

For engineers reviewing the HF920GSE-Z datasheet, HF920GSE-Z pinout, HF920GSE-Z application, or HF920GSE-Z equivalent, this page provides verified technical context, validated pin functions, real-world application constraints, and confirmed alternative options for high-reliability 900V offline regulator selection.

Technical Context

The HF920GSE-Z implements peak-current-mode control with internal slope compensation and leading-edge blanking (tLEB1 = 385ns, tLEB2 = 350ns) to ensure stable regulation under transient load changes and prevent false triggering during MOSFET turn-on spikes. Its proprietary 900V monolithic process integrates the power MOSFET (RDS(ON) = 15Ω @ 25°C) and thermal sensor on-die for precise OTP activation at 150°C with 30°C hysteresis.

Frequency is set externally via FSET resistor (e.g., 200kΩ → 43–55kHz typical), with optional ±3.5% jittering and frequency-doubling mode enabled by adding a 1nF capacitor - doubling fS when FB rises to VOLP (3.3–4.0V), enabling robust operation despite up to 50% transformer inductance drop from magnetizing interference.

Key Specifications

Pinout & Package

HF920GSE-Z is supplied in SOIC8-7A package (8-pin, exposed pad variant), with GND pins assigned to pins 5 and 6 (SOIC8-7A numbering), and D (drain) on pin 8. The package supports 1.3W continuous power dissipation at TA = 25°C (θJA = 96°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP101GSE-Z and UCC28881DR, HF920GSE-Z uniquely combines 900V integration, <30mW standby, on-die OTP, and frequency doubling - making it the only option qualified for utility-grade smart meters and EMI-critical building automation power supplies.

Availability

HF920GSE-Z is available at Aetrix Electronics and suitable for smart meter auxiliary supplies, industrial PLC power modules, large appliance control boards, and home automation gateway power designs requiring stable component supply, long lifecycle support, and guaranteed RoHS/lead-free compliance.

Supply support for HF920GSE-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 design centers in the US, China, and Taiwan, and global manufacturing partnerships.

The HF920 belongs to MPS's high-voltage offline regulator product line, engineered specifically for ultra-reliable, low-standby-power AC/DC conversion in utility infrastructure, industrial automation, and white goods - emphasizing integration, EMI robustness, and thermal precision.

FAQ

What is the maximum continuous output power achievable with HF920GSE-Z in SOIC8-7A package?

At 230Vac±15%, the HF920GSE-Z in SOIC8-7A delivers up to 9.5W output power under TA = 50°C with specified PCB layout (3cm² GND copper). This assumes VOUT = 12.5V, BCM operation at minimum input, and proper thermal derating per θJA = 96°C/W. Exceeding this requires SOIC14-11 or forced-air cooling.

How does the frequency-doubling mode improve reliability in magnetically noisy environments?

When FB voltage reaches VOLP (3.3–4.0V), frequency doubling increases switching frequency by 100%, allowing the converter to maintain regulation even if transformer inductance drops by up to 50% due to external magnetic fields - preventing saturation, overcurrent, and thermal runaway in industrial settings near motors or transformers.

Can HF920GSE-Z operate without an auxiliary winding for VCC supply?

Yes - the integrated HV start-up current source (1–3mA at VD = 400V) powers the IC directly from the drain pin during initial startup. Once VCC reaches VCCH (12–14V), the auxiliary winding takes over. No external start-up resistor or winding is required, simplifying transformer design.

What is the purpose of the PRO pin, and how should it be implemented for input overvoltage protection?

The PRO pin provides external fault shutdown with hysteresis (VPRO = 2.92–3.32V, hysteresis = 0.2V). For input OVP, connect a resistor divider from rectified AC bus to PRO so that PRO exceeds VPRO during overvoltage; the IC latches off until VCC discharges to VCCR (4.8–6.2V), then auto-restarts when the fault clears.

Does HF920GSE-Z require external slope compensation in peak-current-mode control?

No - the HF920GSE-Z includes internal slope compensation optimized for its oscillator frequency and current-sense gain. External slope compensation is unnecessary and would disrupt the built-in loop stability; the datasheet confirms stable CCM/DCM operation across full load and input ranges without added components.

How is burst-mode entry and exit controlled, and what impact does it have on output voltage ripple?

Burst mode activates when FB falls below VBURL (0.4–0.6V) and deactivates when FB rises above VBURH (0.6–0.8V). During burst, the IC alternately enables/disables full switching cycles - resulting in low-frequency envelope ripple (typically ~10–50Hz) on the output, which is acceptable for control logic but may require additional post-regulation for analog rails.

What thermal derating applies when operating HF920GSE-Z above 50°C ambient temperature?

Using θJA = 96°C/W and TJ(MAX) = 150°C, maximum allowable power dissipation drops linearly: PD(MAX) = (150 − TA)/96 W. At TA = 70°C, PD(MAX) = 0.83W (64% of 25°C rating). Layout must maintain specified copper area and airflow; SOIC14-11 (θJA = 70°C/W) is recommended for >70°C ambient.