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AMC3330: sbaa553 voltage divider configuration

Sanghun Kim
Prodigy 20 points
Part Number: AMC3330

Tool/software:

Hello,

I have a question about sbaa553. I'm wondering what would happen if R1' and R2' were moved to the top side as shown in the attached figure. Typically, this type of voltage divider is used for sensing DC link voltage. However, for sensing line-to-line voltage, isolated amplifiers like the AMC3330 take the voltage from the middle resistor. I'd like to understand the difference between these two resistor divider configurations.

Thank you,

  • 0
    TI__Expert 5240 points

    Hi Sanghun,

    I believe the main benefit of having the measurement taken on the middle resistor is that it would be a little more resistant to noise coming from the line.  Having some resistance between the inputs and the line connection helps to attenuate and filter out some noise.   

    The middle resistor sense method is usually done with devices with integrated DC-DC.  When there is a discrete power supply used, with components other than an AMC device using it, present the power supply is usually referenced to the DC- or Neutral nodes, so an AMC device without integrated DC-DC would need to be near that node voltage in order to be powered.

    Thanks.