Analog-digital converter

Abstract

An analog-digital converter includes a decision unit configured to evaluate a comparison potential in a decision step to obtain a comparison result; a number of charging units each comprising a switchable capacitor and an associated reference potential source, wherein each charging unit is configured to change the comparison potential by connecting the reference potential source to the switchable capacitor; and a control unit configure to successively switching one of the charging units following a previous decision step wherein, depending on the obtained comparison result the comparison potential is applied with a predetermined charge by the one respective charging unit, and wherein at least two of the charging units have an associated reference potential source providing different reference potentials.

1 . An analog-digital converter, comprising:
 a decision unit configured to evaluate a comparison potential in a decision step to obtain a comparison result;   a number of charging units each comprising a switchable capacitor and an associated reference potential source, wherein each charging unit is configured to change the comparison potential by connecting the reference potential source to the switchable capacitor; and   a control unit configure to successively switching one of the charging units following a previous decision step wherein, depending on the obtained comparison result the comparison potential is applied with a predetermined charge by the one respective charging unit, and wherein at least two of the charging units have an associated reference potential source providing different reference potentials.   
     
     
         2 . The converter according to  claim 1 , wherein at least two of the charging units each have a switchable capacitor having the same capacitance. 
     
     
         3 . The converter according to  claim 1 , wherein the switchable capacitors of the at least two charging units have the lowest capacitances among the switchable capacitors. 
     
     
         4 . The converter according to  claim 1 , wherein the associated reference potential sources of two of the at least two of the charging units differ by a factor of 2. 
     
     
         5 . The converter according to  claim 1 , wherein the capacitances of the switchable capacitor and the associated reference potential sources of two of the at least two of the charging units are adapted to provide changes to the comparison potential which differ by a factor of 2. 
     
     
         6 . A differential analog-digital converter, comprising:
 a decision unit configured to evaluate a potential difference between two input signal lines in a decision step;   a plurality of charging units for each input signal line each having a switched capacitor unit which is configured to change an input signal line potential on the respective input signal line on application of a reference voltage change;   at least one further charging unit at each input signal line is configured to increase an input signal line potential on one input signal line on application of a first voltage change;   at least another further charging units for each input signal line is configured to decrease an input signal line potential on the respective other input signal line on application of a second voltage change, wherein the sum of the first and the second voltage change equals the reference voltage change;   a control unit configured to:   selectively switch one of the number of charging units at one of the input signal lines depending on a result of evaluating the potential difference between the two input signal lines in a previous decision step; and   selectively switch the one further charging unit at one of the input signal lines and the other further charging units at the respective other input signal line depending on a result of evaluating the potential difference between the two input signal lines in a further previous decision step such that the input signal line potential of the one input signal line is increased and the input signal line potential of the other input signal line is reduced;   wherein the one further charging unit is configured to increase an input signal line potential on the one input signal line on application of the first voltage change and the other further charging unit is configured to decrease an input signal line potential on the other input signal line on application of the second voltage change in the further decision step.   
     
     
         7 . The differential analog-digital converter according to  claim 6 , wherein at least one of the charging units, the at least one further charging unit and the at least one other further charging unit have switched capacitor units having capacitors with the same capacitance. 
     
     
         8 . The differential analog-digital converter according to  claim 7 , wherein the capacitors have the smallest capacitance among the capacitances of the switched capacitor units. 
     
     
         9 . A method for operating an analog-digital converter including a number of charging units, each comprising a switchable capacitor and an associated reference potential source, the method comprising:
 evaluating a comparison potential in successive decision steps to obtain a comparison result; and   successively switching one of the charging units following a previous one of the decision steps, wherein, depending on the obtained comparison result, the comparison potential is changed by the one respective charging unit by connecting the associated reference potential source to the switchable capacitor, wherein in two of the successive switching steps different reference potentials are applied to the switchable capacitor.