Questions about AN-1557 (AD5940 & AD8233)

I want to use EDA (Figure 21.), BIA (Figure 15.), and ECG (Figure 10.) in the AN-1557 document as a mode that works for each mode.

However, common to all three modes, AIN4/LPF0 pin is connected to the ground through CLPF.

EVAL-AD5940BIOZ is used at 4700pF (4.7nF), but I know that 100nF should be used to measure EDA.

Please inquire if there is a CLPF that satisfies both EDA/BIA/ECG.

In addition, we ask if there is a way to select the CLPF value.

Parents
  • +1
    •  Analog Employees 
    on Jun 23, 2020 10:53 AM

    CLPF creates a low pass filter with the internal Rfilter at the output of the LPTIA. The resistor is software configurable and is set to 20Kohm by default in the EDA firmware. This gives a cut off frequency of 1693Hz which is well above the band of interest for EDA. 4700pF is also suitable for BIA.

Reply
  • +1
    •  Analog Employees 
    on Jun 23, 2020 10:53 AM

    CLPF creates a low pass filter with the internal Rfilter at the output of the LPTIA. The resistor is software configurable and is set to 20Kohm by default in the EDA firmware. This gives a cut off frequency of 1693Hz which is well above the band of interest for EDA. 4700pF is also suitable for BIA.

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