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:
May. 31, 1994
Filed:
May. 03, 1993
Gordon L Mortensen, San Jose, CA (US);
National Semiconductor Corporation, Santa Clara, CA (US);
Abstract
A circuit is provided that reduces the electromagnetic emissions from an integrated circuit. The circuit includes the resistive portion of an intrinsic low pass filter network and a means for modulating the resistance in response to switching of the integrated circuit nucleus logic elements. The resistance is increased before the nucleus logic elements switch and is gradually decreased upon completion of all switching of the nucleus logic elements. A portion of the transient switching pulse waveform, normally provided by the external power supply, is instead provided by the intrinsic nucleus capacitance associated with the nucleus logic. In particular the high frequency components are sourced by the intrinsic nucleus capacitance. The amplitude and the rise time of the transient switching pulse is thereby reduced. Further reduction in electromagnetic emission is provided by modified output buffers where transient switching waveforms are reduced by current limiting the output switching transistors and providing initial transient current from the intrinsic capacitance associated with the output buffer.