Dejitter issue

Document created by analog-archivist Employee on Feb 23, 2016
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the IC not outputting any audio signal. approximately one out of every 128
times the IC is enabled, or at the same frequency when certain blocks in the IC
are enabled/disabled.

 

DAU have recently found a bug that affects many of the codecs and SigmaDSPs
that we have designed
in the past couple of years. This bug is in a dejitter circuit that we use on
these products to clean up the
serial port clocks when the IC is operating in both master or slave modes. On
the affected ICs that
include converters (all except the ADAU144x), the bug will manifest itself by
the IC not outputting any
audio approximately one out of every 128 times the IC is enabled, or at the
same frequency when
certain blocks in the IC are enabled/disabled. The affected products include:
ADAU1381
ADAU1382
ADAU1781
ADAU1361
ADAU1761
ADAU1442
ADAU1445
ADAU1446
ADAU1461
ADAU1961

On the ADAU144x, the frequency of occurrence will be much less than 1/128 – to
the point that it’s
unlikely that a customer will ever see it. We of course still recommend that
the work-around is
implemented for the ADAU144x parts, because that will ensure that they never
see the error. It’s
important to note that this bug is something that could appear on any
individual IC; it’s not a case
where one chip will either have it or not have it.

The good news is that we understand the cause of this issue and have
workarounds that users can
implement in their initialization code. This should not require any hardware
redesign. The work-
arounds depend on whether the IC is being used in master or slave mode; we have
different work-
arounds for each case.

The bug is described in the attached errata document, which can be sent to
anyone who is working
with the affected parts. We are working on putting this explanation and the
work-arounds in the
datasheets for these parts, so that any future user of these ICs will see this.

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