Monolithic Power Systems Inc. HF920BGS-Z

Overview

HF920BGS-Z from Monolithic Power Systems is a monolithic 900V flyback switching regulator IC with integrated MOSFET, programmable frequency up to 150kHz, EMI-optimized frequency jittering (±3.5%), and <30mW no-load standby consumption. It delivers up to 10W output power in SOIC14-11 package for AC/DC power supplies in smart meters and industrial controls.

For engineers reviewing the HF920BGS-Z datasheet, HF920BGS-Z pinout, HF920BGS-Z application, or HF920BGS-Z equivalent, key selection criteria include its 900V integrated MOSFET R_DS(ON) (15Ω typ @ 25°C), burst-mode light-load efficiency, VCC UVLO hysteresis (4V), PRO pin protection with auto-restart, and dual-package availability (SOIC8-7A/SOIC14-11) with validated thermal resistance (θ_JA = 70°C/W).

Technical Context

The HF920BGS-Z implements peak current mode control with internal slope compensation and leading-edge blanking (t_LEB1 = 385ns, t_LEB2 = 350ns) to ensure stable operation under transient load steps and transformer leakage spikes. Its feedback loop uses FB pin voltage division (K_DIV = 3.4–3.7) to set primary current limit, enabling precise output regulation across input ranges from 85VAC to 420VAC.

EMI mitigation is achieved via externally programmable switching frequency (via FSET resistor), ±3.5% frequency jittering over 256-cycle carrier, and optional frequency doubling mode triggered at VOLP (3.3–4V) to maintain regulation during magnetizing interference. Thermal protection integrates OTP (150°C threshold, 30°C hysteresis) on the same die as the 900V MOSFET.

Key Specifications

Pinout & Package

HF920BGS-Z is available in SOIC14-11 package (14-pin, 0.150" wide body, 1.27mm pitch). GND pins (1, 2, 7, 8) provide low-impedance return paths; D pin connects directly to high-voltage AC rectified bus; S pin senses primary current through external shunt.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP6004GQ-Z and UCC28632DR, HF920BGS-Z uniquely combines 900V integration, programmable EMI reduction, and on-die thermal protection - making it optimal for high-reliability, wide-input, low-standby applications where board space and component count are constrained.

Availability

HF920BGS-Z is available at Aetrix Electronics and suitable for smart meter power supplies, industrial PLC modules, large appliance control boards, and home automation hub designs requiring stable component supply and long-term lifecycle support.

Supply support for HF920BGS-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 design centers in the US, China, and Taiwan, and global distribution networks.

The HF920B product line targets high-voltage AC/DC conversion for utility-grade and industrial applications, emphasizing EMI robustness, ultra-low standby power, and monolithic integration to simplify high-reliability power supply design.

FAQ

What is the maximum continuous output power achievable with HF920BGS-Z at 230VAC input?

The HF920BGS-Z in SOIC14-11 package delivers up to 10W continuous output power at 230VAC ±15%, tested at T_A = 50°C on a defined 20cm×15cm×10cm test board with 2.5cm² GND copper area. This rating assumes V_OUT = 12.5V, single-output configuration, and BCM operation at minimum input voltage.

How does the frequency doubling mode function, and what triggers it?

Frequency doubling activates when FB pin voltage rises to the overload protection threshold (VOLP = 3.3–4V) for 8192 consecutive switching cycles. With a 1nF capacitor on FSET, the IC doubles f_SW to maintain regulation during transformer inductance loss caused by external magnetic fields - enabling continued operation despite up to 50% inductance reduction.

Can HF920BGS-Z operate safely with 420VAC input?

Yes. The integrated 900V MOSFET and internal start-up current source support input ranges up to 420VAC (≈600VDC bus). Designers must ensure transformer turns ratio and snubber design limit peak drain voltage to <810V (90% of 900V rating) for long-term reliability, per datasheet voltage stress guidelines.

What is the purpose of the NC pin (Pin 13) in the SOIC14-11 package?

Pin 13 is explicitly designated as No Connection (NC) in the datasheet and must remain unconnected. It is not internally bonded and serves no electrical function - connecting it risks latch-up or undefined behavior. Layout guidelines require this pin to be left floating with no trace or pad.

How does the PRO pin provide external protection, and what recovery behavior occurs after fault clearance?

The PRO pin shuts down the IC when voltage exceeds 3.1V (typ), with 0.2V hysteresis. Upon fault removal, V_PRO drops below 2.9V, triggering automatic restart via VCC recharge from the internal HV current source - no manual reset or external circuitry is needed for recovery.

Is HF920BGS-Z RoHS-compliant and halogen-free?

Yes. All MPS parts, including HF920BGS-Z, are lead-free, halogen-free, and fully compliant with the EU RoHS directive. Green status documentation and material declarations are available on the Monolithic Power Systems website under Quality Assurance resources.

What is the recommended minimum input bulk capacitor value for universal input (85–265VAC) operation?

For universal input, use 2μF/W of estimated output power. For high-voltage-only operation (>185VAC), halve the value. At 420VAC, capacitor stacking with balancing resistors (e.g., four 1206 resistors totaling 20MΩ) is required to distribute voltage across series-connected electrolytics, as specified in the application note.