• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 46 subscribers
  • Views 174 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ADC088S102: Channel data seems to be shifted

Kazuki Kitajima
Prodigy 60 points
Part Number: ADC088S102

Dear Sir/Madam,

I would like to confirm the data acquisition with SPI on this device. As attached below, I suppose to get the "FF" from IN0 though, the data shows in the next channel. It seems all data shifted by one bit.

Is this the normal operation result of this device or am I missing the important things such as timing requirement? Please also let me know if you need more information from my side.

PS: I'm going to be out of the office for a few days and will not be able to respond few days. Apologies for the late response in advance.

Best Regards,

Kazuki Kitajima

  • +1
    TI__Mastermind 24970 points

    Hello,

    From what I understand, you are reading data one frame after you expected it.

    Let me explain how the device output data, and we can go from there when you are available. 

    This device has a one frame delay between when the channel is selected to when the data form the respective channel is outputted. 

    Referring to the timing diagram below, lets call the first 16SCLk frame N. In frame N, the SDI address bits select channel 1 to be sampled. Within frame N, the SDO is outputting data from the previous frame, N-1. 

    The next 16 SCLK after, now frame N+1, after the power down period in the timing diagram. This is where the data sample from Channel 1 will be outputted in SDO.

    Hopefully this clears up the device functionality. 

    Regards

    Cynthia 

  • 0 in reply to Cynthia
    Prodigy 60 points

    Hello Cynthia-san,

    Understood. Everything is clear to me now!

    By the way, this kind of one-frame delay spec is common for ADC's SPI communication?

    I'm new to those types of devices so I'd like to know them as future references.

    Best Regards,

    Kazuki Kitajima

  • 0 in reply to Kazuki Kitajima
    TI__Mastermind 24970 points

    Kazuki-san

    The ADC measurement results latency (delay) varies from device to device, as well as by type of ADC (delta sigma vs SAR) 

    Within the TI SAR ADC portfolio, there are devices that do not have any frame delay, and devices that have up to 3 frames delay, thus it really depends on the device and specifications needed. 

    As for Delta Sigmas, these device are a bit more complicated due to the digital filtering inherent to the architecture design.  

    TI has put together a collection of education videos called TI Precision Labs that covers multiple types of devices and topics

    Within this collection there is a topic: SAR and Delta-Sigma: Understanding the Difference, that consist of 4 videos. Each provides the PowerPoint for download as well. I suggest the first two videos to better understand the topic of latency. 

    SAR and delta-sigma: Basic operation

    Digital filters and latency

    Hope this helps,

    Cynthia

  • 0 in reply to Cynthia
    Prodigy 60 points

    Cynthia-san,

    I looked at the document, video a little bit and found really helpful for me.

    Thank you for the answer & for sharing the very useful documents.

    Best Regards,

    Kazuki Kitajima