--- In "charliem_1216" <>
wrote:
>
> Hi --
>
> --- In "j.chitte" <j.chitte@> wrote:
> >
> > Hi,
> >
> > I am struggling a bit to get clean data off the ADC. Sometimes
> > (rarely) it is just a couple of mV bipolar noise, ie 2 LSB on
the 5V
> > unipolar range I am using. This is fine and matches the spec of
the
> > MAX197
>
> It's been a while since I used the MAX197 (project was shelved
...).
Hi, thanks for posting back, I'd given up hope of a reply on this one.
I found mostly the problem was a lose connection on one of my
regulators on the external board. I'm now down to 4mV which is much
more reasonable but probably should be better.
>
> > However, most of the time its 10 or 20 mV which makes a bit of a
joke
> > of the 12bit ADC precision.
> >
> > I was wondering if there is enough external capacitance on the
197
> > Vref.
>
> Looking at the TS-7250 schematic, it seems there isn't any external
> capacitance. The datasheet (as I'm sure you've seen) suggests
4.7uF
> at REF (pin26) and .01uF at REFADJ. Schematic shows .1 and 4.7uF
on
> REFADJ.
Yes , I'd looked into that. I actually think this is a TS
documentation error since there is a capacitor on pin 26 , but since
it is a microscopic smc device I can't tell its value. It seems too
small to be a 4.7uF though!
Since the TS schematic shows it connected to another pin I was not
sure whether I could trust the value shown either.
Their engineering team seem very competant so I think the residual
noise may be from elsewhere but I'm checking everything at this
stage. I'd have been happier if the documentation was accurate.
>
> >
> > Anyone routinely getting better than this?
>
> What test setup are you using? I might be able to dust off my TS-
7250.
>
> Regards, ...... Charlie
>
> >
> > Thanks.
> >
>
I have some op amps buffering my inputs on an external board. They
feed into the 7250 via a ribbon cable.
I was interested to know if I could expect to acheive full 12 bit
accuracy with a bit of care.
Thx
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