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

[prateek_k_chd]

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]

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.

 

[prateek_k_chd]

Alright then. Buffer it is. Thanks !

 

[ALERTLINKS]

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