In a message dated 5/24/01, David Gelfand writes: > When we inject as per IEC 61000-4-6, the 1 kHz tone is demodulated and is > VERY loud in the telephone earpiece! This happens no matter which i/o > cable we inject, even the power cord.
Hi David: While it is not surprising for an unprotected SLIC port to have trouble with the 61000-4-6 test, I think it is abnormal for the problem to be equally pronounced when cables other than tip/ring are being tested. There may be a problem with your ground connections and/or test setup. Are you using CDNs or the clamp method? Do you have a good ground plane as specified in the standard? I recently purchased most of the equipment required to perform this test, and I have been experimenting in the lab to characterize various DAAs and SLICs. I have found that the results I get are somewhat dependent on the specifics of the test setup. The first thing I would suggest is that you review your test setup to be sure it fully complies with 61000-4-6. I have not tested the AM79R70, but I did run some quick tests on a circuit that used the Intersil HC55183, which is also a ringing SLIC. In that test, the SLIC was pretty quiet at carrier frequencies above 1 MHz, but there was some 1 KHz demodulation at lower frequencies. I have not had time to experiment with possible fixes. I do know of someone who is using the AM79R70 and claims that they have passed this test. Unfortunately, I do not know the details. By the way, don't feel too bad if you are having trouble with this test. It is a brutal test, and most people I know who have tested their existing designs have failed. Since passing this test becomes mandatory on July 1 for CE marking, I expect that there will be a lot of activity as the July 1 date approaches. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 http://www.randolph-telecom.com
