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AMC1200: amc1200

Ross Atkinson
Prodigy 60 points
Part Number: AMC1200


Tool/software:

Hi

i am using a acm1200 device to monitor a supply voltage. All is well at ambient, but below -20 get errors (dips) even though the supply is driven from a PSU.

as this a controlling a motor, noise may be the issue. the circuit is similar to the datasheet but optional diff filter caps are not there.

also c2 is 100n and r2 and r3 are 39r. Rshunt is 60R. vdd1 is 5V and vdd2 is 3.3v supplied by own regs, so no zener is required. The output is fed to a diff amp with a gain before being feed to the adc.

I am going to add the C3 and C4 caps (1uF). how import is the filter do i need to reduce any values in resistors and caps?

regards

Ross

  • 0
    TI__Guru 56532 points

    Hi Ross,

    Typically we recommend designing the anti-aliasing filter to have a cutoff frequency of one decade (10x) beyond the sampled signals frequency. 

    The common-mode filtering caps (C3 and C4) should be 10-20x less than the differential cap C2, as tolerance mismatch in the common-mode filtering caps could result in a differential frequency response. 

    In general, increasing resistor values is favorable compared to having larger capacitors since the tolerance is much tighter for a similar price. This will produce more expected results from system-system. 

    Were our sales folks able to get in contact with you?