RE: Re: eQADC operation on MPC5554

Oh, I had expected that would have been the issue.
 
On reading your post again, I don't quite understand - to clarify - you
are performing ADC conversions and the digital result is always off by a
constant factor?  Could you provide some examples of the raw data and
the input voltage.  Does your result clip out at 0 anywhere below 0.9V?
 
Please verify you have VDDA0 and VDDA1 at 5V, Vrh at 5V, Vrl at gnd.
 
Other things to try - perform conversions on the internal refs to see if
they are correct, perform conversions using both ADCs to see if both are
the same, perform without calibration incase you have made an error in
the MAC settings.
 
- Allan

________________________________

From: [email protected] [mailto:[email protected]] On Behalf
Of JVB1_wow
Sent: Tuesday, November 14, 2006 2:12 PM
To: [email protected]
Subject: [MPC500] Re: eQADC operation on MPC5554



Allan,
We have only the 100nF cap not the resistor.
Joe
--- In [email protected] <mailto:MPC500%40yahoogroups.com> ,
"Dobbin Allan-r11834" 
<Allan.Dobbin@...> wrote:
>
> What do you have connected to the REFBYPC pin? You should only 
have a
> 100nF cap to gnd, not a resistor. See EB643 - the resistor was only
> required on very early revs of silicon.
> 
> - Allan
> 
> ________________________________
> 
> From: [email protected] <mailto:MPC500%40yahoogroups.com>
[mailto:[email protected] <mailto:MPC500%40yahoogroups.com> ] On 
Behalf
> Of JVB1_wow
> Sent: Tuesday, November 14, 2006 11:37 AM
> To: [email protected] <mailto:MPC500%40yahoogroups.com> 
> Subject: [MPC500] eQADC operation on MPC5554
> 
> 
> 
> Hello,
> I am designing a system with the MPC5554 micro-controller. We are
> planning on using the eQADC. Checkout of the prototype hardware 
shows
> a large offset voltage of around -0.900V. The measured data in
> perfectly linear just offset by this bias. Anyone seen this before? 
> Thanks.
> 
> Joe
> 
> 
> 
> 
> 
> 
> [Non-text portions of this message have been removed]
>



 


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