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Original question:

slau384

ADS1292R: Schematic error in SLAU384.pdf

Steven Baker
Intellectual 280 points

Part Number: ADS1292R

Hi,

It appears that the NOTES for the schematic have an omission in SLAU384.pdf  

My request is that SLAU384.pdf be corrected to including changing C89 and C90 from DNI to 47 pF capacitors.

Background:

The notes in SLAU384.pdf state

For two channel ECG Do the following modification
1) Mount 51K resistor in place of R71 and R63
2) Mount 0 Ohm resistors in place of C48, C46, C49 and C50
3) Make following components DNI
R66, R64, R72, R62, C47,C45,R70 and R69

This leaves the IN2 inputs with a 51k + 47 pF LPF, while the IN1 inputs have a 51k resistor and no capacitor (there are DNI caps C89 and C90).  Why would the two ECG inputs have different filtering?

In this thread from 2013, David Sun77114 asks, "How about C89 and C90, should be put a 47pF cap there."  

Ryan Andrews responded, "C89 and C90 would provide some low-pass, anti-aliasing filtering for IN1P and IN1N, respectively, in combination with the 51k resistors. 47pF capacitors like the ones used for Channel 2 would give you a cutoff of about 66 kHz"


It's great that the answer is in E2E, but it would be better to have the documentation corrected. Thanks in advance for updating documentation to save other customers the time of trying to understand why the two ECG inputs aren't symmetrical.

Thanks,

Steve

http://www.ti.com/lit/ug/slau384/slau384.pdf

  • 0
    TI__Guru**** 182601 points

    Hi Steve,

    Thank you for the comments! 

    We'll look into what we can do to edit the PDF document or perhaps add a note or errata somehow.  The schematic pages in the SLAU384 document were actually printed from the CAD tool used to create the printed circuit board for that evaluation module, and then inserted as a post process to our regular documentation flow.  We might not be able to change the 'Note:' on page 51 (the old CAD package has been archived), but we may be able to address this some other way.  Give us some time to look into our options and we'll get back to you next week.

  • 0 in reply to Tom Hendrick
    Intellectual 280 points

    Hi Tom,

    Have you had time to see what the options are?

    Thanks,

    Steve

  • 0 in reply to Steven Baker
    TI__Guru**** 182601 points

    Hi Steve,

    Sorry for the delay - Ryan is looking into a way to modify the 'Note:' directly in the PDF.  The original schematic was captured in an old CAD tool that is no longer supported, so this will take a little time to propagate through the system.