An apparatus for providing a clock signal based on a received clock signal includes a time-to-digital converter configured to generate timestamp information based on the received clock signal. The apparatus includes a first filter configured to generate clock period information based on the timestamp information. The apparatus includes a phase monitor circuit. The phase monitor circuit includes a second filter configured to provide a mean period signal of the received clock signal based on the clock period information. The phase monitor includes a phase error detection circuit configured to generate a phase error indicator based on a threshold difference value and a difference between the clock period information and expected clock period information. The expected clock period information is based on the mean period signal.