Advanced Micro Devices, Inc.
Fine granularity in clock generation

Abstract:

An oscillator circuit includes a phase-locked loop (PLL) with a plurality of voltage controlled oscillator (VCO), a clock divider circuit receiving the VCO phase outputs and outputting a first stage clock signal with an adjustable clock period related to the PLL period based on selecting a combination of two of the VCO phase outputs. The first stage clock signal has a balanced duty cycle at frequencies that are related to the PLL frequency by even fractional divisions of the VCO phase output period based on the quantity VCO phase outputs, and an unbalanced duty cycle at frequencies that are related by odd fractional divisions. A duty cycle adjustment (DCA) circuit receives the first stage clock signal selectively adjusts a falling edge of the first stage clock signal to provide an even duty cycle and feeds a resulting signal to the second stage clock signal output.