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TMDXIDDK379D: Unlikely cut-off frequency of QEP channel hardware filter

Intellectual 310 points

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Part Number: TMDXIDDK379D

Hello,

the above mentioned development kit offers the connection of an incremental coder via QEP. The circuit can be found in IndustrialDrivesRev[2.2].pdf on page 11. The document can be found in the ControlSuite under DesignDrive->Development Kits->IDDL379D Kit->Documentation->Hardware Development Package. There, the combination of a 47k pull-up resistor and a 10 nF capacitor is placed on the input lines of the incremental encoder. This combination leads to a cut-off frequency of nearly 340 Hz which seems far to low for these logical signals. The rise times of the encoder signals is far too long to analyze the speed of the connected machine. Does anyone have an idea why this combination of resistor and capacitor is placed there? Is the intention to change them as required by the self chosen encoder?

Thanks

Martin

  • This was done to suppress the ground jitter. Since the signal was driven by a push pull stage, it was not an issue. You may change the values as appropriate.

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