18V rail clamp — 600W peak pulse, DO-214AA
The SMBJ18E3/TR13 is a single-channel Zener TVS diode from Microchip's SMBJ series, designed to clamp transients on 18V DC rails. Its reverse standoff voltage of 18V means it sits across the supply without conducting during normal operation, only shunting when the line exceeds the 20V minimum breakdown threshold. Peak pulse power is rated at 600W for a 10/1000µs waveform, giving a clamping voltage of 32.2V at 18.6A peak pulse current.
The 20V minimum breakdown defines the threshold where the diode starts to avalanche — a 19V rail would keep it off, but a 21V spike triggers conduction. The 32.2V clamping voltage is the maximum voltage the protected circuit sees during the pulse; if your downstream components are rated for 30V absolute max, this part leaves only 2.2V margin, so confirm the load's avalanche capability. The 18.6A peak pulse current is the current the diode can sink at the clamping voltage — a 600W pulse at 32.2V yields that 18.6A, meaning the source impedance of the transient matters for whether the part survives.
The base product number SMBJ18 covers the full voltage family, and the suffix indicates lead-free / RoHS-compliant construction. Availability and lead time are confirmed per RFQ — no allocation constraints reported.
DO-214AA footprint and temperature range
Housed in the DO-214AA (SMB) package, the part is a surface-mount two-terminal device with a cathode band indicating polarity — unidirectional, one channel. The SMB footprint is shared with many TVS diodes in the same power class, so board layout reuse across voltage variants is straightforward.