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Old 12th January 2013
  #127
Quote:
Originally Posted by emitsweet View Post
I don't have 20 years experience. I had an intern job 20 years ago for 5 months while I was in school, it was a 1 semester cop-op thing. I ended up changed majors, I never did electronics. When I worked on semiconductors I was actually a Chem Eng student, I did cv deposition, I switched majors and haven't done any of that since.
So one could possibly say that "I designed AD converters" as a means of support for your opinion was stretching the truth somewhat? I designed loudspeakers whilst at university as part of my course...I wouldn't call myself a loudspeaker designer, I've really only retained the most basic knowledge there. Certainly haven't done anything with it in 10 years.

Quote:
Originally Posted by emitsweet View Post
Regardless, I originally stated there was no noticeable latency between
AUDIO converters I have used.
That might have been what you MEANT, but you missed out the word "noticeable". You've been arguing "no latency" for a couple of pages.

There certainly IS noticeable latency if you parallel the direct source with the round-trip through the converter - you'll hear it as phasing. You've been stating that converters have NO latency from the start - it's only since it's been pointed out that you're wrong have you started adding in the "noticeable". And as I've said from the start, in most cases I agree. But not all - which is why we need to be aware of it, because it COULD cause problems in some circumstances.

Quote:
Originally Posted by emitsweet View Post
I also stated the only latency I knew of with ADC was while encoding and due to clock propagation delay of gates. You claimed "Latency and clocking are not related" with A/D converters, and that's incorrect.

page 19

http://www.ti.com/lit/an/sbaa147b/sbaa147b.pdf


"Figure 14B shows a timing diagram"
This diagram, as far as I understand it, actually supports what I'VE been saying. I've never said that the delay isn't induced during the clocking phase - I've said that changing the clock source from internal to external won't affect the latency, which is what you've stated a few times now. I suppose it MIGHT vary it at the subsample level (I suppose it has to to put 2 converters in sync) but that really is super insignificant even compared to the converter latency.

I don't know if this is a language barrier thing, but if that's what you've been saying all along, then it hasn't been clear.

As an aside, you might like to read the following paragraph on page 19 - I'll quote it here for you to save you hassle:

"For this reason, we measure latency for a delta-sigma A/D
converter by starting at the beginning of a sample period, and measuring to the time that data can be retrieved. It may also be practical to include in the latency time the time needed to retrieve the data, since delta-sigma A/D converters nearly always have serial interfaces. For audio converters, this additional latency can be very significant, even up to several tens of sample periods. For low-speed industrial converters with sinc filters, it sometimes amounts to only a few modulator cycles. For delta-sigma A/D converters, filters with constant group delay are almost always used, so there is no difference between group delay and latency. The latency-time of a delta-sigma converter is often called Settling time."

Surely point proved now - from the horses mouth? Even your "low speed industrial converters" have latency.....