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ADXRS620 Questions

Hi, I just get another three question about the ADXRS620:

1. Based on the figure1  in the data sheet, may I conclude the drive axis utilize the trans-impedence circuit while the sense axis employ the charge amplifier circuit to sense the variation of the weak capacitive signal ?

2. How to understand the unexpected frequency signal around 4kHz in the figure21 (page 8, the noise spectral density) ?

3. If I want to set the circuit gain and bandwidth of the last stage by placing a resistant between the SUMJ and Rateout, what's the type of the circuit, it is inverting amplifier or noninverting amplifier, I guess it should be inverting amplifier, but the functional block diagram confuse me.

thanks

  • Thank you for your comment. I have branched this into a new discussion, since you are posing new questions. 

  • QUESTION

    1. Based on the figure1  in the data sheet, may I conclude the drive axis utilize the trans-impedence circuit while the sense axis employ the charge amplifier circuit to sense the variation of the weak capacitive signal ?

    RESPONSE

    We appreciate your interest, but this is not the right forum for analyzing internal design details of the product.

  • QUESTION

    2. How to understand the unexpected frequency signal around 4kHz in the figure21 (page 8, the noise spectral density) ?

    RESPONSE

    The honest answer is, I don't know.  The purpose of the plot is to make you aware of the noise energy distribution, over the frequency range that is offered. Again, we appreciate your interest, but this forum is for application-level questions, not detailed design review information.  Sorry about that...

  • QUESTION

    3. If I want to set the circuit gain and bandwidth of the last stage by placing a resistant between the SUMJ and Rateout, what's the type of the circuit, it is inverting amplifier or noninverting amplifier, I guess it should be inverting amplifier, but the functional block diagram confuse me.

    thanks

    RESPONSE

    I can see how this might create some confusion. Unfortunately, the original author of this datasheet is not with our company anymore, so we don't have any opportunity to ask for clarification on this. However, I can assure you that the section in the datasheet, which explains how to establish the bandwidth, is correct.

    Great questions! Sorry I am not able to help more, but I hope that this is sufficient for helping you move forward.

  • Thanks for your timely feeback. It help me a lot. I just want to take my application effort one step further. May I ask where I can get the more detailed design details which are not confidential.

  • Check this paper out for some early details on these types of gyroscopes and perhaps do a more thorough search of these particular authors. I hope that helps!

  • Thanks a lot ! Great paper ! I have a lot of respect for the author !