What the 200 V, 4 A rating means for your rail
The STPS4S200UFN is a 200 V, 4 A Schottky rectifier from STMicroelectronics, built for medium-voltage power rectification and freewheeling applications where low forward voltage and fast recovery matter. Its 870 mV forward drop at 4 A keeps conduction losses manageable for a 4 A average rectified current, while the 5 mA reverse leakage at 200 V defines the standby budget in a hold-off scenario. The 175°C junction temperature rating lets it run in high-ambient environments — think sealed power supplies, motor-drive snubbers, or PFC boost stages where airflow is limited.
Obsolete — plan the replacement now
For a BOM already qualified to this footprint, the procurement path is the independent distribution channel — verified surplus stock, last-time-buy remnants, or new-old-stock lots. Date-code provenance matters here; mystery stock surfacing years after the last-time-buy window should be screened for authenticity and storage condition.
The DO-221AC SMA Flat Leads package (SMAflat Notch) is a low-profile surface-mount case that fits standard SMA pad layouts but with a reduced standoff height. The 175°C junction maximum is the ceiling for a Schottky — the thermal pad on the SMAflat is smaller than a traditional SMA, so the PCB copper area and via stitch under the device carry the dissipation. At 4 A continuous, the junction-to-ambient thermal resistance will need a solid pour on the cathode tab side to keep the die below 150°C in practice.