On Mon, 13 Jan 2003, Augusto de Conto wrote:

        > What is the Vref+ and Vref- range
        > for AD conversion?
        >
        > Can I:
        > Vdd = 5V
        > Vss = 0V
        > Vref- = 5V
        > Vref+ = 6V ?
        >
        > Thank
        >
        > Augusto de Conto
        >

> -----Original Message-----
> From: Vasile Surducan [SMTP:vasile@S3.ITIM-CJ.RO]
> Sent: Wednesday, January 15, 2003 8:16 AM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [PIC]: AD Ref
>
> No you can't. Just because of some dummy protective diodes...
>
> see:
> http://www.geocities.com/vsurducan/electro/PIC/f877.html
>
> regards,
> Vasile
> http://www.geocities.com/vsurducan
>
Not to mention that the datasheet defines the limits for the Vref inputs.
e.g. for the 16F877
(AVdd-2.5) < Vref+ < (AVdd + 0.3)
(AVss-0.3) < Vref- < (Vref+ - 0.3)

Regards

Mike



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