AN165 Datasheet (Crystal) - EMI REDUCTION TECHNIQUES

AN165, EMI REDUCTION TECHNIQUES

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

www.DataSheet4U.com AN165 Application Note CS4297A/CS4299 EMI REDUCTION TECHNIQUES 1.

INTRODUCTION 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.

Note that 49.1 MHz is 2 times the CS4297A internal clock frequency of 24.576 MHz.

EMI SHUNTING CIRCUIT The key to reducing common-mode emissions is to add decoupling (called shunting) at the