Patent ID: 8433027

Claim:
A method for a digital audio interface, which doesn't require a handover procedure when switching between audio sources and allowing to switch between audio data sources of unknown rates, comprising the following steps: (1) providing a digital tracking controller that works in conjunction with a first fractional-N loop PLL, which derives a device clock from a master clock; (2) using an I2S protocol comprising a data signal and at least two clocks, wherein a first clock is used as a sampling clock for the data signal and a second clock is used as an I2S word clock to define word boundaries; (3) automatically detecting an incoming I2S rate by completely determining a correct group of I2S rates, wherein said correct group of I2S rates is determined by the digital tracking controller by setting a feedback divide ratio such that a nominal frequency of a VCO of the first PLL is set mid-way between an upper end and a lower end of a determined I2S rate group, wherein the upper end and the lower end of the determined I2S rate group have common internal settings, and a sign of a correction applied to the first PLL is used to distinguish between both upper end and lower end groups of rates; (4) synchronizing the first and second clocks by the digital tracking controller by computing an offset deltax signal that is applied to the feedback divide ratio of the first PLL, wherein said offset deltax signal is computed based on a current phase error between the master clock and the I2S word clock and its derivative; and (5) minimizing a phase error between the first clock and the second clock by deploying the digital tracking controller as another PLL that modifies the feedback divide ratio of the first PLL.