DESCRIPTION
The HCF4521B is a monolithic integrated circuit, available in 16-lead dual-in-line plastic package and plastic micro packages.
The HCF4521B have a chain of 24 flip-flops with an input circuit that allows three modes of operation. The input circuit functions as a crystal or an RC oscillator or as an input buffer for an external oscillator. Each flip-flop performs a divide-by-two function giving a total count of 224 = 16,777,216. The count advances on the negative going edge of the clock. Access is available to the final seven stages giving the device added flexibility.

■ VERY LOW QUIESCENT CURRENT
■ HIGH NOISE IMMUNITY
■ VOLTAGESUPPLYRANGE 3V TO 18V
■ ALL STAGES ARE RESETTABLE
■ RESETDISABLES THE RC OSCILLATORFOR LOWSTANDBY POWER DRAIN
■ RC AND CRYSTAL OSCILLATOROUTPUT ARE CAPABLEOF DRIVING EXTERNAL LOADS