Subject: Re: MPC8272ADS stability issues

From: Dmytro Bablinyuk <[email-masked]>
Date: Tue, 20 Dec 2005 16:22:38 +1100

> 
> Does anyone have any news regarding any resolution of this issue?
> 
We cannot guarantee that this is solution for everybody BUT:
We had similar problems with our MPC8272ADS and this morning we 
discovered that core voltage exceeds recommended values - the core 
voltage on 8272ADS was 1.6V instead of 1.5V.
Where according to MPC8272EC, Rev. 1.2, 05/2005 page 7

--8<--
Table 4. Recommended Operating Conditions

Caution: These are the recommended and tested operating conditions. 
Proper operation outside of these conditions is not guaranteed.

Rating Symbol Value Unit
Core supply voltage VDD 1.425 – 1.575 V
--8<--

We run memory test, as for now, for almost 9 hours and so far without 
problems. Though before board was crashing every 1-4 hours. We don't 
know whether this is source of the problem - we will keep testing it.

Power supply for MPC8272ADS generates ± 5V, ± 12V, +3.3V - they are all ok.
Core voltage is generated by U45 on the 8272ADS board. There is a 
trimmer pot RP1 for adjusting the core voltage - we never checked it 
before since we assumed that it should be set properly by factory. But 
today we found that U45 gives 1.6V instead of 1.5V, which is outside of 
recommended values and datasheet says "Proper operation outside of these 
conditions is not guaranteed".
So, check you core voltage (U45) - it might help.

Dmytro