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CTMU: Do internal parallel current paths exist?

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sjb741
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2019/06/27 04:42:27 (permalink)
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CTMU: Do internal parallel current paths exist?

DS30009743B-page 12
For the higher CTMU ranges, the internal resistances have a significant effect on the calibration, therefore, the High-Current mode calibration is appropriate. The High-Current mode calibration is typically limited to a single device pin with a dedicated connection to the CTMU.
 
 
DS30009743B-page 23      
4.3 Calibration and Measurement Considerations
The chosen resistor value should be at least 100 times the internal resistance to minimize the offsets generated by the internal resistors.
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    du00000001
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    Re: CTMU: Do internal parallel current paths exist? 2019/06/27 05:30:23 (permalink)
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    sjb741
    The High-Current mode calibration is typically limited to a single device pin with a dedicated connection to the CTMU ...

    ... (refer to the specific device data sheet for more information) !
     
    https://www.microchip.com/stellent/groups/SiteComm_sg/documents/DeviceDoc/en542792.pdf
    http://ww1.microchip.com/downloads/en/appnotes/ctmu%2001375a.pdf
     
    Basically, the resistances between individual devices pins and the CTMU input may differ (due to different metallization path lengths, # of vias etc.). THUS the hint that the calibration is typically valid only for the pin that has been used during calibration.

    PEBKAC / EBKAC / POBCAK / PICNIC (eventually see en.wikipedia.org)
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    sjb741
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    Re: CTMU: Do internal parallel current paths exist? 2019/06/27 06:07:03 (permalink)
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    OK - Thanks.
     
    I should have read the next section (DS30009743B-page 23: 4.4 Measuring Internal Resistance) before posting...
    The device is then configured for current measurement, but the I/O pin is driven low. When the measurement is taken, the measured voltage is the drop across the internal resistance.
     
    So that makes sense, the concern is over internal voltage drops forming part of the measurement.
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    du00000001
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    Re: CTMU: Do internal parallel current paths exist? 2019/06/27 06:10:57 (permalink)
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    sjb741
    So that makes sense, the concern is over internal voltage drops forming part of the measurement.

     
    That's - in other words - what the document already stated:
    DS30009743B
    ... the internal resistances have a significant effect  ...


    PEBKAC / EBKAC / POBCAK / PICNIC (eventually see en.wikipedia.org)
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