Crystal AN165
The CS4297A and CS4299 AC ’97 audio codecs are based on a new and faster fabrication process, and certain precautions in the analog I/O circuitry may be required to prevent 49.1 MHz commonmode radiation. The shunt capacitors must be connected to a "clean" (free of digital noise) I/O ground.| Part No. | AN165 |
|---|---|
| Datasheet | AN165 Download |
| Manufacturer |  Crystal |
| Description | EMI REDUCTION TECHNIQUES |
| Buy | Stock & Price |
DESCRIPTION
Common-mode radiation is the result of undesired voltage drops due to voltage differentials in the I/O ground system. The CS4297A clock transitions result in a rush of current that may induce the digital ground plane to "bounce". When external speaker or microphone cables are connected to the audio system, any common-mode voltage potential on the analog ground will drive the cables (antennas) and radiate electric fields. The magnitude of the electric fields are the result of the I/O cable length (the antenna) and the magnitude of common-mode current. P.O. Box 17847, Austin, Texas 78760 (512) 445 7222 FAX: (512) 445 7581 Copyright © Cirrus Logic, Inc. 2000 (All Rights Reserved) MAY ‘00 AN165REV1 1 AN165 4. PCB LAYOUT CHECKLIST● Connect analog and digital ground together with a 1/16 inch trace under the CS4297A. A direct connection between analog and digital ground will reduce the differential-mode radiation and improve the EOS (Electrical Overstress) capabilities of the CS4297A.
