ULTRA LOW POWER ANALOG TO DIGITAL CONVERTER

An analog-to-digital converter for ultra low power applications, such as pacemakers, has a digitizer for producing a digital output signal from a sampled analog input signal. The digitizer is normally in off state to save current. A sample-and-hold circuit stores a plurality of successive samples of the analog input signal. A control element turns on the digitizer in response to an activation signal, sequentially applies the stored samples to the digitizer in response to the activation signal and thus reconstructs the signal as it existed prior to the activation signal.