1.5h is generally enough in Santiago. There are often very long lines in the domestic check-in/bag drop area, so if you see them just tell the personnel that you're getting late -- they'll let you cut the line. Same applies to the return trip: the bottleneck is immigration in the LATAM Elite area (security is very fast) or security in the general boarding area (passport control is fast): if you feel you're getting late, tell the agents. There is additional security control just before you board the plane, but once they've scanned your boarding pass it's not a problem.

I've never missed a connection in SCL even with a 1h long layover. I go there a few times a year