The T1635-800G-TR: Gate trigger current is 35 mA maximum, and gate trigger voltage is 1.3 V maximum. The 35 mA hold current means the triac stays latched once triggered as long as the load current stays above that threshold.
Package and mounting — what to check on the board
The D²Pak (TO-263-3) is a surface-mount package with a large tab for thermal and electrical connection. The tab is internally connected to the MT2 terminal, so the PCB copper pour must be electrically isolated or at MT2 potential. Cut Tape is also available for prototype quantities.