The 1.5KE400A-B: Housed in the DO-201AA / DO-27 axial-lead package (supplier device package DO-201), it mounts through-hole on a PCB or terminal block. The 342 V reverse standoff voltage means it begins conducting only when the line exceeds that threshold, so it stays invisible to the protected circuit under normal operating conditions.
Key clamping parameters and what they mean for your circuit
The clamping voltage is the voltage the protected equipment sees during a surge — a 548 V clamp means downstream components must have a voltage rating above that level to survive a worst-case event. With a 342 V reverse standoff (working voltage), this part is a natural fit for 277 VAC or 300–350 VDC bus protection. Note that power line protection is not supported — this is a secondary-side transient suppressor, not a primary AC mains protector. It is intended for DC rails, signal lines, and low-impedance secondary circuits where the surge energy is limited.
Lifecycle reality — obsolete, sourced through independent channels
Diodes Incorporated lists the 1.5KE400A-B as obsolete. The part is available through independent surplus and broker distribution, with quantities and pricing confirmed at the time of an RFQ. Availability is lot-specific and confirmed at quote time — no stock-holding claim, no deferred lead-time number.