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dhutchison1945
Visitor II
April 26, 2011
Question

STM8L151K4 adc input impedance

  • April 26, 2011
  • 3 replies
  • 670 views
Posted on April 26, 2011 at 10:13

STM8L151K4 adc input impedance

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    3 replies

    L
    lowpowermcu
    Visitor II
    May 17, 2011
    Posted on May 17, 2011 at 15:12

    Hi spectre,

    In the datasheet, I have found

    RAIN: External resistance on VAIN. It is equal to 50 KOhm.

    I think it the input impedance you are looking for.

    D
    dhutchison1945Author
    Visitor II
    May 17, 2011
    Posted on May 17, 2011 at 15:12

    Dear lowpowermcu,

    no,the rain(50kohm max) is the external resistor that you add in order to limitate the input current.

    I want to know the adc input pin impedance,but I think that I can see only the leakage current.

    b.r.

    spectre

    F
    fggnrc2
    Visitor II
    May 17, 2011
    Posted on May 17, 2011 at 15:12

    Hello Spectre!

    I agree with you: I found only the leakage current which is mainly due to the internal ESD protection diodes.

    You have also to take into account the current which the ADC draws in the sampling phase. This current depends on the input capacitance, whose value can be found in the datasheet too.

    However, leakage current is usually a few microamps, so you can estimate ADC input resistance as one MOhm.

    Regards,

    EtaPhi

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