Clock multiplexing system

A clock control circuit in an integrated circuit for providing a differential clock signal to a differential clock tree. The clock control circuit includes: first differential multiplexers configured to select first outputs from the input clock signals; second differential multiplexers coupled to the first differential multiplexers and configured to select second outputs from the first outputs; loop back signal lines configured to feed back the second outputs to at least part of the input clock signals of the first differential multiplexers; and differential signal lines of the differential clock tree coupled to the second outputs.