Monolithic Power Systems Inc. HF920GS

Overview

HF920GS from Monolithic Power Systems is a monolithic 900V flyback switching regulator IC with integrated MOSFET, designed for high-reliability offline AC/DC power supplies operating from 85–420V_AC. It delivers up to 10W output power in SOIC14-11 package, features programmable fixed-frequency control (up to 150kHz), active burst-mode operation (<30mW no-load consumption), and on-die over-temperature protection synchronized with the 900V power switch - enabling robust smart meter and industrial control power designs.

For engineers reviewing the HF920GS datasheet, HF920GS pinout, HF920GS application, or HF920GS equivalent, key selection considerations include its 900V drain rating, VCC UVLO hysteresis (4V), FB-based burst-mode threshold (0.5V), frequency-doubling capability under overload, and SOIC14-11 thermal resistance (θ_JA = 70°C/W) for thermally constrained board layouts.

Technical Context

The HF920GS implements peak-current-mode control with internal slope compensation and leading-edge blanking (t_LEB1 = 385ns, t_LEB2 = 350ns) to ensure stable operation across wide input ranges and transformer tolerances. Its proprietary 900V monolithic process integrates the power MOSFET (R_DS(ON) = 15Ω @ 25°C) and thermal sensor on the same die, enabling precise junction-temperature-triggered shutdown at 150°C with 30°C hysteresis.

Frequency programming is achieved via a single resistor on FSET (e.g., 200kΩ sets f_S ≈ 49kHz), with optional 1nF capacitor enabling frequency-doubling during OLP events - allowing continued regulation despite up to 50% inductance drop from external magnetic interference. Protection logic includes time-based OLP (8192-cycle counter), auto-restart SCP (V_SCP = 1.5V), and VCC OVP (25.5V) with 70μs delay.

Key Specifications

Pinout & Package

HF920GS is housed in a SOIC14-11 package (14-pin, 7.5mm × 8.75mm, 1.27mm pitch) with exposed thermal pad connected to Pin 5 (GND). The package provides θ_JA = 70°C/W and θ_JC = 35°C/W on a 4-layer PCB per JESD51-7, supporting continuous 10W output at T_A = 50°C with 2.5cm² copper GND area.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP6004GS-Z and UCC28881DR, HF920GS uniquely combines 900V integration, sub-30mW standby, and frequency-doubling - making it the sole option for high-reliability, magnetically noisy, wide-input applications where transformer derating and thermal accuracy are non-negotiable.

Availability

HF920GS is available at Aetrix Electronics and suitable for smart meter auxiliary power, industrial PLC controllers, and large-appliance main power supplies requiring stable component supply across 10+ year product lifecycles and extended temperature operation (-40°C to +125°C).

Supply support for HF920GS 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 20 years of expertise in monolithic high-voltage integration and energy-efficient power conversion.

The HF920GS belongs to MPS's high-voltage offline regulator product line, engineered specifically for reliability-critical AC/DC power supplies in utility infrastructure, industrial automation, and white goods - where 900V integration, ultra-low standby, and magnetic immunity are mandatory.

FAQ

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

The HF920GS delivers up to 10W continuous output power under 230V_AC ±15% input when mounted on a SOIC14-11 test board with 2.5cm² GND copper area at T_A = 50°C. This rating assumes single-output 12.5V configuration, BCM operation at minimum input, and proper transformer turns ratio (N = 5) to limit V_DS stress below 810V.

How does the frequency-doubling mode activate and what design benefit does it provide?

Frequency-doubling activates automatically when FB voltage rises to the OLP threshold (3.65V) for 8192 consecutive cycles - indicating sustained overload. The switching frequency doubles (e.g., 49kHz → 98kHz), allowing the converter to maintain regulation despite up to 50% reduction in transformer inductance caused by external magnetic fields, such as those near motors or solenoids.

Can HF920GS operate safely with input voltages exceeding 420V_AC?

No. The absolute maximum drain voltage is 900V, corresponding to a peak rectified input of ~594V_DC. At 420V_AC, the peak is ~594V_DC; exceeding this risks avalanche breakdown. Designers must ensure surge protection (e.g., MOVs, TVS) limits transient peaks to ≤850V_DC to maintain 100V safety margin per IEC 62368-1.

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

The PRO pin provides external fault detection with 3.1V threshold and 0.2V hysteresis. For input OVP, connect a resistor divider from rectified DC bus to PRO, sized so that PRO reaches 3.1V at the desired trip point (e.g., 450V_DC). Upon trigger, HF920GS shuts down and auto-restarts once VCC discharges to 5.5V, enabling fail-safe recovery without manual reset.

Does HF920GS require an external current-sense resistor, and what is its typical value range?

Yes. An external sense resistor between S pin and GND sets the primary peak current limit. With V_CSL = 0.97V max and target peak current of 0.5A–1.2A, typical values range from 0.82Ω (for 1.18A limit) to 2.2Ω (for 0.44A limit). The resistor must be non-inductive, rated for ≥1W pulse power, and placed adjacent to S/GND pins to minimize noise coupling.

How does the integrated 900V startup current source function during initial power-up?

At power-on, the internal high-voltage current source (I_Charge = 2mA typical) draws from the D pin to charge the VCC capacitor. Once VCC reaches VCCH = 13V, the IC begins switching and disables the HV source, transitioning to auxiliary-winding supply. If VCC drops below VCCL = 9V (e.g., during brownout), the HV source re-engages to sustain operation.

Is HF920GS RoHS-compliant and halogen-free?

Yes. HF920GS is lead-free, halogen-free, and fully compliant with the EU RoHS Directive 2011/65/EU. All packaging materials meet IPC/JEDEC J-STD-020 moisture sensitivity level 3 (MSL3), and the device carries MPS's green status certification per their Quality Assurance documentation.