The STMicroelectronics BYW99PI-200RG is a dual-diode common-cathode fast recovery rectifier in a TOP-3I insulated through-hole package. The 200 V reverse voltage rating and 20 µA leakage at 200 V suit it for 48 V telecom rails and 110 Vdc intermediate buses, with margin for transients.
The BYW99PI-200RG is officially obsolete per STMicroelectronics. For new designs, a pin-compatible alternative in the same TOP-3I package should be evaluated. No last-time-buy window remains — the surplus channel is the only supply path.
The TOP-3I insulated package eliminates the need for an isolation pad between the diode tab and the heatsink, which simplifies assembly and improves thermal transfer. The through-hole mounting suits point-of-load rectifier stages on single-sided or mixed-technology boards where reflow isn't an option for the power devices.