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TIDA-010232: How is the resistance value of the selected resistor determined in the design

Vayne Li
Expert 1010 points
Part Number: TIDA-010232
Other Parts Discussed in Thread: AMC3330

Tool/software:

Hi Teams,

There is no specific reason for selecting the resistance value of the resistor in this design. I would like to know why such a resistance value is needed. Can you explain it?

It's the resistance values of these resistors, for example, at 800V, the voltage divider resistor is 280k Ω and the sampling resistor is 250 Ω. How is this resistance value determined

  • 0
    TI__Expert 4400 points

    Hi,

    Thanks for reaching out. 
    The resistors are chosen in that way, because accuracy of measuring RisoN/P is best when RstP/M is in a similar range. Thats why RstP/N is selceted similar to the critical RisoN/P values.
    The critical values are 100Ohms/V and 500Ohms/V. This translates to 40kOhms to 200kOhms for r 400V systems. That is why we selected RstP/N =68.1kOhms for 400V.
    For 800V the critical values are 80kOhms and 400kOhms,  That is why we selected 280kOhms for RstP/N.
    The sampling resistor is selected to limit the input voltage at AMC3330 to 1V.

    Best regards,

    Andreas