Post Go back to editing

# CN0532 circuit diagram LPF

Category: Hardware
Product Number: EVAL-CN0532-EBZ

Hello, in the "Figure 1. Complete ADXL1002 with IEPE Compatible Circuit Diagram" of the Circuit Note CN-0532 (Rev. 0), resistors R6, R8, capacitors C4 and C5 are indicated but not mentioned afterwards. I've checked as well the User Guide.

I want to confirm if these corresponds to a LPF on the analog signal? If so, what is the cut out frequency of that filter?

typo corrected
[edited by: FelipeCook at 1:10 AM (GMT -4) on 11 Aug 2023]

## Top Replies

• yes, that is a cascade of two RC low pass filters. Here is a Matlab script I put together to visualize the filter response. You can see there the filter transfer function. The -3dB cut off…

• Thank you for posting your question in this forum.  Just wanted to make sure that I am identifying the part of the circuit that you are referring to, correctly.  Can you confirm? • Hi, thanks for your answer. Yes, that is the part of the circuit I refer to. It is shown in the Figure, but not mentioned in the document.

I want to confirm if that correspond to a low pass filter on the analog signal? If so, what is the cut out frequency of that filter?

Regards,

• Hi  ,

yes, that is a cascade of two RC low pass filters. Here is a Matlab script I put together to visualize the filter response. You can see there the filter transfer function. The -3dB cut off should be near 14kHz.

```%% RC values
R1 = 680;
R2 = 1.3e3;
C1 = 4.7e-9;
C2 = 4.7e-9;
s = tf('s');
Hs = R2/((1+s*R2*C2)*(R1+R2+s*R1*R2*C1)-R1);

%Bode plot
options = bodeoptions;
options.FreqUnits = 'Hz'; % or 'rad/second', 'rpm', etc.
bodemag(Hs, options)
grid on``` I hope this helps,

Pablo.

• Thank you, Pablo!

Your response showed me a different way to do Bode plots, in the Matlab environment.

Mark

• Thanks Pablo.

I think it is important ADI puts this information in the description of CN0532 (for example this limits the ability to go beyond 14 kHz as suggested in ADXL1002 user guide, not a problem in my case, I actually appreciate the LPF).