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I have a problem with my design with ads7952. The chip is configured to work in manual mode. I think the correct procedure is that I specify the channel I would like to sample in the current frame. Then I will get the data in the next frame. However, I noticed that the chip always send out the channel data I specified TWO frames before. I am running the SCLK at 10MHz, and I put in a long delay between samples. I dont think I am violating any timing spec. Thank you.
The ADS7952 is working as expected according to your description. This operation is often found confusing to others who have used this device. The two frames come from the following operations:
1) There is a 1-frame delay from sampling data until the data out is read in the following frame.
2) There is also an additional 1-frame delay between writing/configuring the selected channel to when the MUX actually switches to that channel.
In total, this accounts for a two frame delay between selecting an input channel and reading out the sampled data on that channel.
Here is an image to help clarify:
I hope this helps clear up the confusion. Let me know if you have any more questions with this part!
Christopher Hall | Δ-Σ Data Converter ApplicationsTI.com | TI Precision Designs | Selection Guide | Technical Documents | Tools & Software | Design Notes | E2E Site Map
This definitely explains the results I got. I think this diagram really helps user understand the whole mechanism. It should go into the data sheet more than anything.
Thank you for the feedback, we'll try to clarify the data sheet for you and others down the road...
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