Patent ID: 7221299

Claim:
A method of converting an analog input signal into a digital output signal using an analog-to-digital converter system, the analog-to-digital converter system having a first stage analog-to-digital converter and a second stage analog-to-digital converter, the method comprising: measuring a characteristic of the analog input signal; varying a characteristic of a digital test signal in response to the characteristic of the analog input signal; and inserting the digital test signal into the analog-to-digital converter system; wherein varying a characteristic of the digital test signal in response to the characteristic of the input signal includes: confining an input swing of the digital test signal between zero and a negative test signal voltage when an amplitude of the analog input signal is above a positive reference voltage, and confining the input swing of the digital test signal between zero and a positive test signal voltage when the amplitude of the analog input signal is below a negative reference voltage.