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AMC1400: remote current sensing

David Fishman
Intellectual 475 points
Part Number: AMC1400

Hello,

My application needs to have the AMC1400 placed on one board while the current sense resistor is placed on another board.

The two boards are conencted by a cable. The cable will carry the VDD1, GND1, INP and INN signals.

I know that it is recommended to connect the input RC filter near the INP/INN pins, and I can do that.

Is there any restriction on the length of cable between the AMC1400 and the current sense resistor?

Thanks,

Dave

  • 0
    TI__Guru 51211 points

    Hi Dave,

    Out of curiosity, what type of application is this for and how long of a cable do you have in mind? 

    How will the VDD1 supply be generated? 

    In general, it is preferable to have the AMC device and high side supply circuit close to the shunt resistor, then route the differential output over long traces/connections. As the input voltage range of the AMC1400 is relatively small, 250mV, routing this signal over a long distance may allow HV switching noise from operations to couple to the input, reducing accuracy. The output voltage swing is +/-2.05V and the noise on the low side of the device is typically much lower magnitude. For your proposed configuration, I recommend adding common-mode filter capacitors from each input to ground, 10-20x smaller in magnitude compared to the differential filter capacitor. Additionally, it is important that any transient overvoltages are applied to all of the high side device pins at the same time. If a fault were to occur somewhere in the high voltage domain, the high side supply must able to follow the transient within a short period of time to ensure the device is not damaged. 

  • 0 in reply to Alexander Smith
    Intellectual 475 points

    Hello Alexander,

    Thank you for your response.

    This application is for a HV and low current power supply, where the sensing circuits are isolated from the HV lines. The cable would be less than 1 foot long. I was think of using a UCC12051 to generate VDD1.

    Dave 

  • 0 in reply to David Fishman
    TI__Guru 51211 points

    Hi Dave,

    Happy to help - I think this will be fine. Happy to do a schematic and/or layout review when you are ready. 

  • 0 in reply to Alexander Smith
    Intellectual 475 points

    Thanks, that's really nice of you to offer!

    Take care,

    Dave