SFFS889 July 2024 TMS320F2800132 , TMS320F2800133 , TMS320F2800135 , TMS320F2800137
PLL lock functionality is implemented by comparing the difference (error) between the feedback clock and reference clock through phase frequency detector (PFD). When PLL is in lock and generating the correct frequency, the difference is < 100pS to approximately 300pS. Once there is any fault causing the PLL output frequency to drift, the difference goes outside of that range. In such a case, PLL lock signal goes from 1 to 0 indicating PLL is out of lock. DCC can detect that drift has occurred.