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ADS1299: Lead-OFF current sources in ADS1299

Part Number: ADS1299


We have ADS1299 based custom board. We want to measure the impedance of patients body. For that we are using AC lead off detection functionality of ADS1299. 

As datasheet tells AC lead off current source accuracy is ±20%. So we have implemented a logic to calibrate the current source on channel one for better accuracy.

We have some queries related to AC lead off detection -

1. Does ADS1299 has current source available on each channel? (8 current sources)

2. Do we need to perform current source calibration on each channel for better accuracy? 

Thank you.



  • Hi Nikint,

    Thanks for the post. Please see my comments below for your questions.

    1. Yes, each input channel (INxP and INxN) has its current sources.

    2. We do not have the channel-to-channel lead-off current matching specification in the datasheet. The primary usage of the DC/AC lead-off circuitry is to detect lead on or off conditions and is not intended to measure the patients' body impedance accurately. It is a plus to perform current source calibration on each channel if you need better accuracy.



  • Hi TC,

    Thanks for the information. We will try to implement calibration logic for all channels.