| CPC H03L 7/08 (2013.01) [G01R 31/31707 (2013.01); G01R 31/31711 (2013.01); G04F 10/005 (2013.01); H03L 7/00 (2013.01)] | 20 Claims |

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1. A circuit, comprising:
a time-to-digital converter (TDC), configured to receive a first signal having an identification and a first frequency, and output a digital signal associated with the identification of the first signal; and
an evaluation circuit, coupled to the TDC and coupled to a phase-locked loop (PLL) external to the circuit, the evaluation circuit being configured to evaluate the identification of the first signal based on a transition between a first voltage level and a second voltage level of the digital signal.
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