Integrated circuit having a filter with charge balancing scheme to reduce transient disturbances

An apparatus, comprising:

• an input and an output, the output being dependent upon the input, and upon a capacitive value of a variable capacitance circuit,
• the variable capacitance circuit comprising:
• a plurality of capacitive means;
• a plurality of switch means each for selectively coupling corresponding ones of the plurality of capacitive means with other ones of the plurality of capacitive means, thereby selectively changing the capacitive value of the variable capacitance circuit,
• each of the switch means inducing a transient current in the variable capacitive circuit when selectively coupling the corresponding ones of the plurality of capacitive means;
• and
• compensation means for generating a compensating current of substantially equal and opposite magnitude as the transient current, to thereby substantially cancel effects of the transient current at the output upon switching of each of the switching means.

A method of operating a variable capacitance circuit to reduce noise at an output thereof, the variable capacitance circuit including a plurality of capacitive devices and a plurality of switches that selectively couple the capacitive devices with each other, the method comprising:

• providing a compensation device corresponding to at least one switch of the plurality of switches;
• applying a control signal to render the at least one switch conductive,
• the control signal inducing a transient current in the variable capacitance circuit;
• and
• applying a compensation signal to the compensation device, concurrently with the application of the control signal to the at least one switch, to generate a compensation current of substantially equal and opposite magnitude to the transient current, to thereby substantially cancel the effects of the transient current at the output of the variable capacitance circuit.