Silicon Laboratories Inc.
Wide range glitchless switchable clock divider with modified 2/3 divider stages

Abstract:

A divider includes 2/3 divider stages that may be turned off without toggling to extend the divide range of the divider while also reducing the impact of spurs on the divider output, and preserving the timing margin to update the divide ratio glitchlessly. A 2/3 divider stage responds to an input enable signal being deasserted and a modulus input signal being asserted to remain in a disabled state in which the divider stage does not toggle by ensuring storage elements outputs in the divider stage remain constant. The divider further selects an update clock for the divide ratio of the divider utilizing an output from a most downstream stage that remains enabled.