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ADS1299EEGFE-PDK: 9V peak to peak at output of ADS1299 when using Lead Off Detection

Khanh Huynh
Prodigy 20 points
Part Number: ADS1299EEGFE-PDK
Other Parts Discussed in Thread: ADS1299

Hello,

I testing function Lead Off Detection of ADS1299. I configure the Dev kit as below:

Lead off current 6uA
Ac lead-off detection at 31.25Hz
Gain = 1
LOFFP1, LOFFN1.

When I short P&N channel together, I can see 120mV peak to peak at the output of ADS

But when I disconnect P&N channel. I saw the output voltage swing between +4.5V and -4.5V. How can it happens? I think the output voltage should swing between VDD and VSS. My supply voltage is +2v5 to -2v5.

Looking forward for your answer.

Thanks

  • 0
    TI__Genius 11550 points

    Hi Khanh,

    Welcome to the E2E forum!

    It looks like your attachment image did not come through properly. Can you please re-upload the image for our reference?

    Thanks.

    -TC 

  • 0 in reply to TCT
    Prodigy 20 points

    Hi TCT,

    Thanks for your reply,

    I would like to send the picture of measurement again.

    This is the output voltage when I short P&N Channel together:

    And this is the output voltage when I disconnect P&N Channel:

    My configuration is

    As I knew that the input voltage can span from -VREF / Gain to + VREF / Gain. But how about the output voltage?

    In this case, when I disconnect the P and N channel, how is the current loop in the IC?

  • 0 in reply to Khanh Huynh
    TI__Genius 11550 points

    Hi Khanh,

    Thanks for posting the measurement plot for our reference.

    We'll get back to you this week. 

    Thanks.

    -TC