TransZorb® 1.5kW bidirectional TVS — obsolete but still spec'd into BOMs
The 1.5KE16CA/54: This is a bidirectional device — one junction handles both polarities, so a single part protects a signal pair or a DC rail that sees reverse transients.
What the ratings mean for the board
The 22.5 V clamping voltage at 66.7 A is the ceiling the diode holds the line to during a 10/1000 µs surge — downstream components rated for 25 V or higher survive this event. A 12 V nominal rail with 10% tolerance stays at 13.2 V max, so this TVS sits just above the regulation band and does not clip normal operation. Peak pulse power of 1500 W at 25°C derates linearly with ambient temperature. At 125°C the derating factor is roughly 60%, so the effective capability drops to about 900 W — still adequate for most IEC 61000-4-5 surge levels on a 12 V supply. The axial DO-27 body conducts heat into the leads; the trace copper area on both sides of the board acts as the heatsink.
Obsolete — sourcing through independent channels
Vishay lists the 1.5KE16CA/54 as obsolete. The part is available through independent surplus and broker channels — each lot is date-code and quantity specific, confirmed at RFQ time. No pin-compatible second source is documented, but the 1.5KE series footprint (DO-201AA/DO-27) is shared across many TVS vendors; a functional replacement requires verifying the breakdown and clamp voltages match the BOM line.