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:
Jun. 24, 2008
Filed:
Feb. 05, 2003
Daniel Saufu Mui, San Jose, CA (US);
Daniel SauFu Mui, San Jose, CA (US);
ZiLOG, Inc., San Jose, CA (US);
Abstract
A keypad encoding circuit contains a voltage dividing network and an integrated circuit. The voltage dividing network includes a string of resistors that generates an encoding signal voltage. The integrated circuit converts the encoding signal voltage into a digital value indicative of which of the keys has been pressed. The cost of the voltage dividing network is reduced by forming the resistors from a layer of conductive carbon and avoiding the cost of providing discrete resistors. Each resistor has the same resistance even where the dimensions of the conductive carbon patches that form the resistors vary. Providing the resistors does not involve additional manufacturing cost because the resistors are made in the same step as are the landing pads of the voltage dividing circuit. Manufacturing costs associated with etched printed circuit board layers are avoided because inexpensive printed layers are used to realize the required traces and resistors.