The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 09, 1997
Filed:
Feb. 12, 1996
Thomas J Meany, Limerick, IE;
Patrick R Hickey, Limerick, IE;
Analog Devices, Inc., Norwood, MA (US);
Abstract
A clock oscillator having a pair of pins adapted for coupling to an external crystal, a first one of such pair of pins being adapted for coupling to an external clock. A switch, formed on the chip, is provided for electrically decoupling the crystal excitation circuit from one of the pair of pins in response to a control signal. In accordance with one embodiment of the invention, the switch is disposed between the output of a crystal excitation circuit and the second one of the pair of output pins and, in another embodiment, the switch is placed in circuit between the input to the crystal excitation circuit and the first one of the pair of pins. In each of these embodiments, when the switch is in a first condition, clock pulses are prevented from being coupled to the second one of the output pins, either: by preventing the external clock from feeding the input to the crystal excitation circuit; or, by preventing the output of the crystal excitation circuit from feeding the second one of the pair of pins. With such an arrangement, when the external clock is used and fed to the first one of the pair of pins, clock pulses are electrically prevented from appearing at the second one of the pair of pins. Therefore, current will not flow from the crystal excitation circuit into any stray capacitance at the second one of the pins.