A digital cardiotachometer ASIC

Abstract

A circuit has been designed which measures the beat-to-beat heart-rate in humans, accepting as input a digital signal representing the subject's pulse. The range of heart-rate covered is 30-255 beats/min. The design is based on an inverse-time counter implemented using a pair of 8-bit down-counters and the associated state determining combinational logic. It also incorporates the logic for a latched 3-digit LCD decoder/driver interface in addition to an 8-bit binary output. The IC has been designed for full testability with bidirectional access to key timing and control points being provided and a scan path strategy applied to the main blocks of the chip. Various test and access modes are controlled using a decoding/multiplexing principle. The IC was designed using the 2.4 /spl mu/m CMOS Mietec cell library and Cadence EDGE software. It contains 13,000 transistors and occupies a silicon area of 25 mm/sup 2/.