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[SOLVED] [PIC16F] Vref for ADC - buffering ?

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prateek_k_chd

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I plan to use Vref+ & Vref- of the ADC of 16F877A. The voltages for these come from a potential divider and hence are high impedance.

So,will placing a 0.1 uF cap on their pins (to store charge) be enough for the ADC? Or do I need to buffer these voltages first ?

PIc's DS says the ADC cap is about 120pF.So I'm guessing the cap could do. But it would be great if anyone can speak from experience !

Thanks a lot !!
 

barry

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I would buffer it. According to the datasheet, the Vref input has two levels, 5uA and 150uA, of input current; this will affect your voltage divider, and caps won't help that error.
 

ALERTLINKS

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Impedence of the circuit should be less than 10K ohms.
 

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