Hi Neil, Jan-Erik.

I think that 11 Tad is for conversion only, the acquisition time is a delay
*before* conversion...
=A0
Best regards,
=A0
Philippe Paternotte
=A0
> Neil wrote 2012-05-13 16:16:
> > Hi all,
> >
> > I'm tinkering with an 18F23K22 and the A/D has changed a bit from the
> > 16F devices I've used previously.  This A/D can now automatically
> wait
> > for the holding capacitor to charge, rather than manually waiting the
> > required charge time as before.  But I'm confused how to set this.
> >
> > I'm using this datasheet --
> > http://ww1.microchip.com/downloads/en/DeviceDoc/41412E.pdf
> >
> > The second paragraph of 17.1.4 explains that the acquisition time
> will
> > be done automatically with this newer A/D, and says it can be set
> > anywhere from 2 to 20 Tad.  But 17.1.5 explains that a full 10-bit
> > conversion required 11 Tad.  So why is Tad configurable from 2 to 20?
>=20
> If you need the higher speed and can live with the slightly lesser
> precision, I guess.
>=20
> And with a lower source imp then the specified 5, 10 or 20 kohm (or
> whatever it is on these devices), it might be OK with a shorter Tacq
> anyway.
>=20
> The main point is that you do not (efter configuring) have to time this
> Tacq in your code at each conversion.
> >=20
> > IE: what would be by reasoning for setting it anything other than say
> 12Tad?
> >
> > In my specific example, I'm running at 16Mhz, so from Table 17-1 I'll
> > use Fosc/16 or Fosc/32, giving me 1.0us or 2.0us Tad.  But then I set
> > Tacq to 12 Tad again, right?
> >
> > Only reason I can see for the Tad adjustability is that it allows for
> > source impedances that are higher or lower than the ideal range...
> ???


--=20
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