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:
Oct. 07, 2014
Filed:
Sep. 01, 2011
Xiaobao Wang, Cupertino, CA (US);
Bonnie I. Wang, Cupertino, CA (US);
Chiakang Sung, Milpitas, CA (US);
Khai Q. Nguyen, San Jose, CA (US);
Xiaobao Wang, Cupertino, CA (US);
Bonnie I. Wang, Cupertino, CA (US);
Chiakang Sung, Milpitas, CA (US);
Khai Q. Nguyen, San Jose, CA (US);
Altera Corporation, San Jose, CA (US);
Abstract
Circuits, methods, and apparatus for dynamic control of source and termination impedances. One output stage provides a series termination when transmitting and a parallel termination when receiving data. A pull-up device has a nominal impedance of 50 ohms when the output stage pulls a pin from a low voltage to a high voltage, while a pull-down device has a nominal impedance of 50 ohms when the pin is pulled from a high voltage to a low voltage. Both the pull-up and pull-down devices are turned on when receiving data. Due to their non-linear current-voltage characteristics, the pull-up device appears as 50 ohms when the pin voltage is higher than one half the supply voltage, while the pull-down device appears as 50 ohms when the pin voltage is lower than one half the supply voltage. The pull-up and pull-down devices can be calibrated to provide a nominal 50 ohm impedance.