Patent ID: 7142819

Claim:
A method of controlling noise in a pulse width modulation circuit comprising: selecting between first and second operating modes; in response to an input signal received in the first operating mode: generating at the sample frequency a data sample stream, wherein each sample within the data sample stream represents a level within a range of information level; and encoding the data sample stream into a stream of pulse width modulated data patterns at the sample frequency, wherein encoding the data sample stream generates noise at a frequency proportional to the sample frequency; and in response to an input signal received in the second operating mode: generating at another sample frequency another data sample stream, wherein each sample within the another data stream represents a level within another range of information levels, and wherein the another sample frequency differs from the sample frequency and the another range of information levels differs from the range of information levels; and encoding the another data sample stream at the another sample frequency into a stream of pulse width modulated data patterns at the another sample frequency, wherein encoding the another data stream generates noise shifted to a frequency which is an integer multiple of the another sample frequency.