US Patent 7196651 Analog-to-digital converter (ADC)

The present invention shows a high speed ADC which can be implemented easily and with low cost into a pure digital integrated circuit. This is realized by converting the analog input voltage into a pulse signal and measuring the pulse signal in length with the help of a delay line and an edge detector. With an XOR gate the input pulse can be converted into two pulses of different lengths. With a special calculation circuitry the digital output value becomes independent of the reference frequency used.