The ’90 is a 4-stage ripple counter containing a high speed flip-flop acting as a divide-by-two and three flip-flops connected as a divideby- five counter.

DESCRIPTION — The ’90 is a 4-stage ripple counter containing a high speed flip-flop acting as a divide-by-two and three flip-flops connected as a divideby- five counter. It can be connected to operate with a conventional BCD output pattern or it can be connected to provide a 50 duty cycle outpu