What this dual-series diode brings to the board
The Infineon BAV99SE6433HTMA1 is a small-signal switching diode in a 2-pair series configuration — two standard diodes connected anode-to-cathode inside a single SOT-363 package. It's rated for 80 V reverse voltage and 200 mA average rectified current per diode, with a fast 4 ns reverse recovery time. That trr figure is the headline here: it makes this part a clean fit for high-speed clamping, snubbing, and steering applications where a general-purpose 1N4148-style diode would leave too much stored charge in the loop. The series pair arrangement is handy for building a dual-rail ESD clamp or a bridge rectifier leg with fewer components, though at 200 mA it's strictly signal-level work — not a power rectifier.
4 ns trr — the spec that matters for switching
A 4 ns reverse recovery time means this diode can switch off fast enough to handle clocked signals in the low-MHz range without excessive ringing or power loss. For comparison, a standard 1N4148 is typically around 4 ns as well, but the BAV99S series gives you two matched pairs in one package, saving board area and reducing parasitic inductance from long traces between discrete diodes. If your circuit is snubbing a relay coil or clamping a fast data line (RS-485, CAN, LVDS), the 4 ns trr keeps the recovery spike short. The 150 nA leakage at 70 V reverse bias is tight enough for most battery-powered designs, though at 150°C junction the leakage will climb — derate accordingly if the part sits near a hot regulator.
Obsolete — sourcing reality
The BAV99SE6433HTMA1 is marked obsolete by Infineon. That means no further factory production runs; the only channel is surplus inventory or broker stock. If you have an active BOM line with this order code, you need a qualified replacement or a last-time-buy buy. The base product number is BAV99S, and Infineon still produces active variants in the same family (e.g., BAV99S, BAV99) in SOT-23 and SOT-363 packages — but the exact suffix E6433 HTMA1 is gone. For a drop-in replacement, look for any BAV99S in SOT-363 from Infineon or a second-source like Nexperia or ON Semiconductor, but verify the pinout and electrical specs against your design.
Package and field-swap note
The SOT-363 (SC-88, 6-VSSOP) package is small — about 2.1 mm x 2.0 mm — and the Infineon PG-SOT363-PO variant uses a leadless plastic package. That means hand-rework on a field site is possible with a fine-tip iron and flux, but it's tight. Orientation is marked with a pin-1 dot on the package top. If you're swapping this on a customer site without a hot-air station, pre-tin the pads and use a tweezer — it's doable, but the small pitch (0.65 mm) means a short is easy. MSL is not specified in the record, but SOT-363 is typically MSL 1; still, bake before reflow if the reel has been open past floor life.