Clamping voltage and the protected rail
The SMBJ28A-13 is a 600 W peak-pulse Zener TVS in the SMBJ series from Diodes Incorporated. Its 28 V reverse standoff voltage means the protected rail can run at 28 V DC without the diode conducting in standby — leakage stays negligible below the breakdown knee at 31.1 V min. When a transient hits, the device clamps at 45.4 V maximum while conducting 13.2 A peak pulse current (10/1000 µs waveform). That clamp voltage is the number the downstream IC's absolute-max rating must clear; if the IC is rated 40 V, this TVS leaves no margin.
Package and board integration
The SMB footprint is a standard reflow profile — no moisture sensitivity level beyond typical JEDEC levels, and the junction temperature range spans -55 °C to 150 °C, covering industrial and under-hood automotive ambient conditions. Unidirectional configuration: cathode connects to the protected rail, anode to ground.