Patent ID: 7576670

Claim:
A sigma delta analog/digital converter for an xDSL multi standard input stage for converting an xDSL signal into a digital output signal, wherein the sigma delta analog/digital converter ( 1 ) comprises: (a) an analog loop filter ( 6 ) which filters an analog difference signal between the xDSL signal to be converted and a feedback signal in order to produce a filter output signal; (b) a quantizer which quantizes the filter output signal from the analog loop filter ( 6 ) in order to produce the digital output signal; and (c) a first digital/analog converter ( 16 ) which converts the digital output signal into the analog feedback signal, and further wherein the analog loop filter ( 6 ) has at least two resonator filter stages ( 6 a , 6 b ) which respectively comprises a first integrator ( 6 a 1 ; 6 b 1 ) and a second integrator ( 6 a 2 ; 6 b 2 ) connected in series thereto, wherein the second integrator ( 6 a 2 ; 6 b 2 ) can be connected to the first integrator ( 6 a 1 , 6 b 1 ) by means of a controllable feedback switch ( 6 a 3 , 6 b 3 ) adapted to close a local feedback loop, and the integrator outputs can respectively be connected by means of a controllable switch ( 25 ) to a signal input of an adder ( 27 ) which adds the output signals from the integrators in order to produce the filter output signal.