Device identity and protection profile
The 1.5SMC220CA-E3/57T: This makes it a fit for 185 VDC or 130 VAC nominal lines where the steady-state voltage stays under the standoff threshold.
The bidirectional channel is a single die in this two-terminal package — polarity is irrelevant on the PCB, which simplifies layout for AC or floating lines. The wide Tj range also means derating at elevated ambient is less aggressive than with a 125°C-rated part.
For a BOM line requiring this exact clamp voltage and package, the 1.5SMC220CA-/57T is the direct order code with no substitution needed.