The STMicroelectronics VIPER100 is a monolithic flyback switching regulator from the VIPER™ series, integrating a 620 V avalanche-rugged power MOSFET with a PWM controller in a single Pentawatt-5 HV package. It delivers up to 100 W in isolated flyback topologies, with built-in soft start, frequency control, and an enable pin for external on/off control. The 8 V to 15 V supply range and 11 V start-up threshold make it straightforward to bias from a simple auxiliary winding. Fault protection includes cycle-by-cycle current limiting and thermal shutdown — no external sensing network needed for basic protection. The switching frequency goes up to 200 kHz, which lets the designer shrink the transformer core compared to 100 kHz designs, though the trade-off is tighter magnetics design and higher switching losses.
The VIPER100 is marked obsolete by STMicroelectronics.
620 V breakdown and 100 W — sizing the power stage
The 620 V breakdown voltage on the internal MOSFET gives headroom for universal-input AC-DC flyback converters (85–265 VAC) with a reasonable reflected voltage and leakage spike margin. At 100 W output, the part is suited for applications like auxiliary power supplies in industrial equipment, battery chargers, and white goods — not for high-power multi-kW stages. The Pentawatt-5 HV package's bent and staggered leads improve creepage distance across the isolation barrier compared to a standard DIP, which matters for the 3–4 kV isolation requirement in offline supplies. Switching up to 200 kHz means the transformer can be wound on a smaller ferrite core than a 100 kHz design, saving board area and height. The trade-off is increased MOSFET switching losses and higher EMI — the soft-start and frequency control features help manage inrush and spread the noise spectrum, but a well-laid-out snubber and input filter are still needed.