Crystal oscillator with controlled duty cycle

Details Crystal oscillator with controlled duty cycle Crystal oscillator with controlled duty cycle

1998-04-28

2000-02-22

Mis, David

Oscillators

Combined with particular output coupling network

Space discharge or unilaterally conductive device in output...

331158, 331175, 331176, 327175, H03B 536, H03B 504, H03B 100, H03L 100, H03L 102

Patent

active

060284919

ABSTRACT:
An oscillator circuit having a first node oscillating with a first indeterminate duty cycle and having a second node oscillating with a predetermined second duty cycle. Both nodes oscillate at similar frequencies. A variable current source and a switch are coupled in series between Vcc and ground with the output of the variable current source being the second node. The first node controls the switch, which is closed when the first node is at a first logic state and is opened when it is at a second logic state. During each cycle, a monitoring circuit measures the time span that the first node is at the first logic state and adjusts the magnitude of the variable current source to make it directly proportional to the measured time span. By adjusting the variable current source, the second node can be made to reach a desired voltage level in a desired amount of time during each cycle. In a second embodiment, a current limiting transistor is inserted between the second node and the switch. The current limiting transistor is controlled by the monitoring circuit and is made to reduce the influence of the switch on the second node as the duty cycle of the first node approaches the predetermined second duty cycle.

REFERENCES:
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patent: 4544897 (1985-10-01), Ishikawa
patent: 5081428 (1992-01-01), Atriss et al.
patent: 5081429 (1992-01-01), Atriss et al.
patent: 5349311 (1994-09-01), Mentzer
patent: 5457429 (1995-10-01), Ogawa et al.
patent: 5477180 (1995-12-01), Chen
patent: 5481228 (1996-01-01), Badyal
patent: 5546055 (1996-08-01), Klughart
patent: 5907254 (1999-05-01), Chang
Erica A. Vittoz et al., "High-Performance Crystal Oscillator Circuits: Theory and Application", IEEE Journal of Solid-State Circuits, vol. 23, No. 3 (Jun. 1988) pp. 774-783.

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