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AMC1311EVM: Applied input decreases as I connect input signal to the analog evaluation module

Sagar Chavan1
Prodigy 20 points
Part Number: AMC1311EVM
Other Parts Discussed in Thread: AMC1311

Hello everyone,

I am using AMC1311EVM analog evaluation module. As per the datasheet the input range to AMC1311 is 0-2V. 

I have used potential divider to get voltage within specified range. (Approx. 1.8 V)

But, When I connect my input to the analog evaluation module and measure it on input side it decreases to 0.6V. 

May I know what is the reason behind it?

Thanks in advance.

  • 0
    TI__Guru**** 168865 points

    Hi there Sagar!

    Welcome to our e2e forum!  Without knowing exactly how you configured this potentiometer for use with the AMC1311EVM, I'm going to go out on a limb and assume that you did not account for the 10K ohms to ground via R4 on the EVM.  This would setup a divider that may account for the input voltage you are seeing.  If you did account for R4, then please provide a little more detail on your setup and we'll take it from there.

  • 0 in reply to Tom Hendrick
    Prodigy 20 points

    Respected Sir,

    Thanks for the reply. 

    I realised that the voltage gets divided because of R4.

    As I want to to measure 600 volts DC using voltage divider circuit R1=6 MOhms and R2=13 KOhms. I am getting 1.944 volts output across R2.

    When I apply this to J1.1 and J1.2 of AMC1311 EVM module, voltage gets dropped to 0.847 volts due to Resistor R4.

    So is it necessary to keep resistor R4 in my case?? 

    Can I desolder resistor R4? 

     

  • 0 in reply to Sagar Chavan1
    TI__Guru**** 168865 points

    Hi Sagar,

    The 10K resistor (R4) on the EVM connects to GND1 of the AMC1311.  In your comments above, you mention R1 and R2 - assuming these are the R1 and R2 positions on the EVM, then you are putting your 13K in parallel with R4.  That would form ~5.6K ohms.  You can remove R4 and tie R1 and R2 into J1, or choose different resistors for R1, R2 and R3 leaving R4 in place.