Vishay lists the 1.5SMC400AHE3_A/H as obsolete. For existing BOM lines that require this exact part number, supply is managed through independent distribution channels — quantities are lot-specific and confirmed at RFQ. No pin-compatible direct replacement from Vishay is documented. Any replacement candidate must match the DO-214AB (SMC) footprint and the unidirectional clamping characteristic to avoid a board spin.
The SMC footprint is larger than the SMA/SMB siblings, providing a lower thermal resistance path for the 1500 W pulse — the copper pad area under the cathode tab directly sets the junction-to-ambient thermal impedance during the transient event. No power line protection is claimed, meaning this TVS is intended for signal or low-power rail clamping rather than AC mains or high-current DC bus suppression. The single unidirectional channel suits DC rails where polarity is fixed.