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:
Sep. 21, 1993
Filed:
Oct. 21, 1991
Shunsaku Ueda, Carlsbad, CA (US);
Silicon Systems, Inc., Tustin, CA (US);
Abstract
The present invention is a constant current source whose magnitude is proportional to capacitor values, reference voltage and input frequency. A frequency divider provides a plurality of signals to one of a plurality of capacitor switches located within a charge generator. The outputs of the capacitor switches are combined to provide a known charge Q.sub.i to an output generator at regular intervals, t.sub.0 =1/F.sub.in. The output generator produces an output current I.sub.out =Q.sub.i /t.sub.0 =C.sub.i *V.sub.bg *F.sub.in, where C.sub.i is a capacitor value, V.sub.bg is a reference voltage, and F.sub.in is the input frequency. A controller provides a control signal to the output generator to limit variations in the output current I.sub.out. The preferred embodiment may be used in conjunction with process invariant circuits in a variety of semiconductor technologies: CMOS, Bipolar, BiCMOS and GAS. In one embodiment, the present invention is used in conjuction with a timer/delay circuit. In another embodiment, the present invention is used in conjunction with a calibration circuit to compensate for various inaccuracies in component performance.