Clamping performance and the 40V rail it protects
The 1.5SMB47A: Its 44.7V minimum breakdown ensures the device stays out of conduction during normal operation, while the 64.8V maximum clamp at 23.5A peak pulse current (10/1000µs waveform) limits the voltage spike seen by the downstream silicon.
Package, footprint, and the DO-214AA reality
The surface-mount body suits reflow assembly on a standard telecom or power-supply PCB. Power line protection is not listed — this is a signal-rail or low-impedance bus clamp, not a primary AC mains protector.