Time counting circuit and pulse signal generating method

Abstract

There is provided a small-size time counting circuit which measures time with high accuracy and low power consumption. Around a differential inverter ring composed of an odd number of differential inverters of identical structure connected in a ring configuration, signal transition is caused to circulate by oscillation. A first signal group is composed of normal output signals from the odd-numbered differential inverters and inverted output signals from the even-numbered differential inverters, which rise and fall sequentially at equal time intervals corresponding to delay times in the individual differential inverters. A second signal group is composed of inverted output signals from the odd-numbered differential inverters and normal output signals from the even-numbered differential inverters, which similarly rise and fall sequentially at equal time intervals. Accordingly, even when the rise time of an output signal from each of the differential inverters composing the differential inverter ring is different from the fall time thereof, the use of the first and second signal groups provides equal increments of time for time measurement.