The Infineon BAV 99S H6827 is a dual series switching diode in a SOT-363 surface-mount package. The 4 ns reverse recovery time qualifies it for high-speed switching applications such as logic-level clamping, snubbing, and general-purpose signal steering on densely populated boards.
The 80 V reverse voltage (Vr) and 200 mA forward current (Io) set the operating envelope for this diode pair. In a typical 5 V or 3.3 V logic rail, the 80 V headroom provides ample margin for inductive kickback or transient spikes, but the 200 mA per-diode limit means it is not intended for power rectification — stay within that average current for continuous duty. The 4 ns trr is the headline switching spec: it ensures clean, fast turn-off in circuits switching at hundreds of kilohertz to low megahertz, such as flyback snubbers or high-speed data-line protection. Leakage current is specified at 150 nA at 70 V reverse bias, which is typical for a standard silicon switching diode. In battery-powered or high-impedance sense circuits, that leakage is negligible at room temperature, but it doubles roughly every 10 °C rise — budget accordingly if the junction sees sustained temperatures near the 150 °C maximum. Forward voltage drop is 1.25 V maximum at 150 mA forward current. That is a bit higher than a Schottky diode at the same current, but the 4 ns trr is faster than most Schottky alternatives, so the trade-off favours switching speed over forward drop in this design.
Because this part is obsolete, any new design should plan for a form-fit-function replacement. The SOT-363 footprint is widely used across the BAV99 family, so a pin-compatible alternative from the same series is the natural cross-reference — see the FAQ for the direct replacement question.