170V rail protection – what the ratings mean
The 170V reverse standoff voltage is the maximum continuous DC voltage the diode blocks without conducting — match it to your nominal rail voltage. At 170V, the diode sits off the rail and only fires when a surge pushes the line above 189V breakdown. Peak pulse power is rated 600W for a 10/1000µs waveform. That translates to a clamping voltage of 275V at 2.2A peak pulse current. For a 170V rail, the 275V clamp means downstream components need a voltage rating at least 20% above 275V — 330V or 400V rated caps and semiconductors are typical.
Housed in a DO-214AA (SMB) package, the part is surface-mount.
Microchip lists the SMBJ170AE3/TR13 as Active.