Upon what maximum airspeed is the instrument approach criteria for a helicopter based?

Explanation

AIM 10-1-2 says that, unless otherwise specified on the chart, 90 KIAS is the maximum speed on Copter instrument approaches, and helicopters using the visibility reduction on conventional approaches must slow to no more than 90 KIAS at the missed approach point. 90 knots is also the upper limit of approach Category A, on which helicopter criteria are based.