Distorted o/p in EXC_OUT Signal from EVAL-AD2S1210SDZ

I am trying to use EVAL-AD2S1210SDZ to read the angle of a resolver. But when I checked the o/p Excitation signal in CRO, I am not getting a sine signal . I am getting a clamped distorted signal.

I am using the op-amp AD8397 with 0.866 gain. 

Can someone please help me to understand why not getting the exact signal at output.

  • 0
    •  Analog Employees 
    on Feb 26, 2021 1:59 PM 1 month ago

    Hi,

    We'll contact the product owner to assist you on this.

    Thanks, Jellenie

  • +1
    •  Analog Employees 
    on Mar 2, 2021 1:19 AM 1 month ago

    tpsamuel,


    Can you please indicate what the position settings are for LK701 - LK703 and LK503?

    Please also verify you see 12V at U4 and U9 pins 8.

    Also can you please indicate what load you have connected to EXC and EXCB outputs at connector J6.

    This information should be sufficient to let me know where the problem might be.

    Sean

  • Hi,

    The issue on the excitation waveform resolved.

    I measured across resolver initially. Later got correct waveform by putting a high resistance.

    Now I want to know What is the maximum exciation voltage we can generate using this Board. We have a resolver which needs 4.25 Vrms exciation.

    I am using AD8397 ( LK14 to LK17 in position B) .Can you please let me know What is the maximum output voltage I can get using these configuration and How I can achieve it?

  • 0
    •  Analog Employees 
    on Mar 2, 2021 4:48 PM 1 month ago in reply to tpsamuel

    tpsamuel,

    If your resolver requires 4.25VRMS (differential) then that is about 6Vp (12Vpp).   The RDC swings between 7.2Vpp to 8.0Vpp differentially, natively which means you would need about 1.5x gain so the 15.4K option should be sufficient for your needs (LK10, LK12, LK14, LK16 = B),   As you are using the AD8397 path if you need a bit more gain you can always use OPTION A on LK10 and LK12 and R10 and R30 to increase the gain but you'll need to be mindful of the output limit with regards to headroom and footroom for the amplifier which roughly is 0.5V on either side with respect to the rail at 100 ohm load.  The issue is that you only have 2.5V of offset through that path.  You may be better off going through the AD8662 path to ensure distortion free operation.   The principle would be the same in that if you measured the peak output from each of EXC/EXCB you could calculate the correct gain and implement in the AD8662 stage.

    Sean

  • We have verified the differential output between EXC abd EXC/ and its coming between 7.8 to 7.9 Vpp.

    So that section is working fine. But after that we connected jumpers LK10 to LK14 to position B and selected AD8397 and when we checked the output by connecting load resistance, we are not getting the voltage expected (multiplied by 1.54) . We are getting very less value. Do you know the reason for that or am i doing anything wrong.

    Can you please provide any detail document on this board as I am having only User Guide