An analog to digital converter includes a resistive ladder outputting a
plurality of reference voltages and a coarse ADC receiving the reference
voltages and a voltage input. A plurality of coarse comparators receive
an output of the coarse ADC. A switch matrix receives an output of the
coarse ADC and the reference voltages. The switch matrix inputs a
plurality of control signals for selecting at least two voltage
subranges. A fine ADC receives the two voltage subranges and the voltage
input. A plurality of fine comparators receive an output of the fine ADC.
An encoder converts outputs of the coarse and fine comparators to a
digital representation of the voltage input. The voltage subranges are
adjacent. Each control signal includes a plurality of control lines for
controlling corresponding switches. The switches are field effect
transistors.