Ring oscillator with constant 50% duty cycle and...

Details Ring oscillator with constant 50% duty cycle and... Ring oscillator with constant 50% duty cycle and...

2007-06-12

2007-06-12

Mis, David (Department: 2817)

Oscillators

Ring oscillators

C331S175000

Reexamination Certificate

active

11191830

ABSTRACT:
Methods and circuits for chain ring oscillators having a constant duty cycle and being insensitive to ground noise have been disclosed. The ring oscillator generates n outputs with 360°
phase shift and each stage is delayed byT2×n.The output of a suitable stage is selected so that a digital XOR-gate, using the output of a selected stage and the output of the nth stage, eliminates variations of the duty cycle caused by temperature and process variations. In case a 50% duty cycle is desired the stage number N of the selected stage can be calculated using the equation N=(n−1)/2. The duty cycle can be varied by selecting the output of another gate. A D-flipflop, clocked by the output of the XOR-gate removes noise from the clock pulses.

REFERENCES:
patent: 5744992 (1998-04-01), Baumann
patent: 5869992 (1999-02-01), Sekino
patent: 6181123 (2001-01-01), Jou et al.
patent: 6650191 (2003-11-01), Branch et al.
patent: 6683504 (2004-01-01), Abernathy
patent: 6727764 (2004-04-01), Manku et al.
patent: 6825644 (2004-11-01), Kernahan et al.
patent: 6828866 (2004-12-01), Liu
patent: 6917224 (2005-07-01), Han

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