The limitations associated with the DAC in a successive-approximation ADC can be avoided by using the analog method of charging a capacitor with a constant current; the time required to charge the capacitor from zero to the voltage of the input signal becomes the digital output. When charged by a constant current the voltage on a capacitor is a linear function of time and this characteristic can be used to connect the analog input voltage to the time as determined by a digital counter.

Tue Jul 13 16:55:15 EDT 1999