Patent ID: 6121811
Filing Date: 2000-09-19
Classification: H03K

Abstract:
A high resolution variable time delay circuit for producing a desired delay time equal to a coarse delay time added to a fine delay time, said coarse delay time being an integer multiple of a clock period T and said fine delay time being not greater than said clock period T, said circuit comprising:a discrete-valued variable current source that produces a current that is proportional to an input integer value F;a first capacitor charged by said discrete-valued variable current source for a duration of time set by said clock period T to provide a threshold voltage;a second capacitor having an initial charge and connected to have said initial charge changed by said discrete-valued variable current source after a delay equal to said coarse delay time, to provide a ramping voltage; and,a comparator connected to said first capacitor and said second capacitor for comparing said ramping voltage with said threshold voltage and for providing an output signal when said threshold voltage and said ramping voltage are substantially equal, to produce a delayed signal with a delay time within T/F seconds of said desired delay time.