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ADS1299-4: Bias and SRBx pin configuration for 4 channel EEG

Tharaka Ratnayake
Prodigy 10 points
Part Number: ADS1299-4

Hi!

First of all sorry for my lack of knowledge about ADS1299-4 as User guide is unclear to me.

So this is my question is about pin configuration in BIAS and SRB1 and SRB2

  1. the ground electrode should be connected to BIAS pin
  2. Other four channels should be connected to INPx pins
  3. SRB2 pin can be used to route one signal from any INPx pins using register configurations.
  4. SRB1 pin routes an external signal to all of the inverting channel inputs.

Are those correct? I'm having a big doubt.

  • 0
    TI__Guru 66406 points

    Hello Tharaka,

    Thank you for your post and welcome to our forum!

    1. The bias electrode is not necessarily ground. Rather, the DC common-mode of that signal is typically set to mid-supply.
    2. All four channels can be treated as differential inputs for A-to-D conversions. What you connect to INxP and INxN depends on the signals of interest in your application. For single-ended (or pseudo-differential) measurements, you can connect a DC common-mode voltage to INxN and apply your input signal to INxP. The ADC on each channel will convert the differential voltage times the gain in the PGA.
    3. SRB2 brings any one INxP input signal out of the device. This has multiple possible use cases in bio-potential applications
    4. SRB1 can route a common signal to all INxN inputs. This is often used in EEG when all electrodes are referenced to a single common input.

    Best regards,