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AMC1311EVM: AMC1311EVM

Abinaya C
Prodigy 70 points

Part Number: AMC1311EVM
Other Parts Discussed in Thread: TINA-TI, AMC1311


Hi
I am seeing a VCM is given to the non inverting terminal of Opmp.I am thinking that is to shift the output voltage.
In my case ,I don't need to shift the output voltage (differential to single ended output).So that can I ignore this VCM circuit.

I simulated without VCM circuit with analog ramping input,but the output was not as expected(which should be difference of differential input voltage).But VCM circuit output voltage is as almost ok as expected

Could be please say whether VCM circuit is necessary and the importance of it. Without VCM circuit ,how should I design the circuit.


Same kind of circuit in below link too:
www.ti.com/.../sbaa229b.pdf

  • 0
    TI__Genius 10797 points

    Hi Abinaya,

    Thank you for your question! Here is a similar post which includes a TINA-TI simulation with VCM tied to GND which may help:

    As explained in the Tech Note you attached and this post, the purpose of the VCM circuit is so the output common-mode voltage can be adjusted to fit the input needs of the ADC it is being interfaced with. This slide-set shows some different ways the AMC1311 output may be used: AMC1311_5F00_DIFF2SE.pdf.

    I hope this helps!

    Best,

    Samiha

  • 0 in reply to Samiha Sharif
    Prodigy 70 points

    Hi 
    Samiha Sharif


    Thanks for sharing these details. I understood that VCM circuit is based on ADC. But still I need some clarification.
    I am using high voltage input(Vin) to AM1311 with a voltage divider to input and I am converting differential ended output to single ended (Vout) using an opamp with some gain without addition VCM .But I am facing difficulty in accuracy between the VIN(high voltage ) and Vout(Single ended output).In simulation there is 16v difference between input and output(i.e. when I give 0V as input (VIN), single ended output is around 50mV (max) with gain &  30mV without gain).One more thing I noted is accuracy was is larger(not good) in low voltage(Like 0 to 15v input) and good in higher voltage (Input given is pulse).I need better accuracy .Is there any way to reach better accuracy.

  • 0 in reply to Abinaya C
    TI__Genius 10797 points

    Hi Abinaya,

    Thanks for your response. Could you please share your schematic and/or simulation results? It would help me understand the issue better. Thanks!

    Best,

    Samiha