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Entry  Thu May 13 19:14:27 2010, Hao Huan, DVDD Problem of DRS 4 
    Reply  Fri May 14 08:40:14 2010, Stefan Ritt, DVDD Problem of DRS 4 
       Reply  Tue May 18 01:47:59 2010, Hao Huan, DVDD Problem of DRS 4 
          Reply  Tue May 18 08:23:07 2010, Stefan Ritt, DVDD Problem of DRS 4 
             Reply  Wed May 19 02:24:12 2010, Hao Huan, DVDD Problem of DRS 4 
                Reply  Wed May 19 09:16:02 2010, Stefan Ritt, DVDD Problem of DRS 4 
                   Reply  Fri Jun 18 11:31:20 2010, Jinhong Wang, DVDD Problem of DRS 4 
                      Reply  Fri Jun 18 11:45:18 2010, Stefan Ritt, DVDD Problem of DRS 4 
                         Reply  Sat Jun 19 10:09:18 2010, Jinhong Wang, DVDD Problem of DRS 4 
Message ID: 81     Entry time: Fri May 14 08:40:14 2010     In reply to: 80     Reply to this: 82
Author: Stefan Ritt 
Subject: DVDD Problem of DRS 4 

Hao Huan wrote:

Hi Stefan,

    on our board some DRS chips draw a lot of current through DVDD after power-up and heat up significantly--it is true that our board doesn't have weak pull-down resistors at DENABLE and DWRITE output pins of FPGA, so this problem might have been caused by that, but a reinitialization of the Domino circuit doesn't help either. We tried different capacitors at DVDD and it seemed the larger the capacitance, the better the result--with a capacitor larger than 10nF some of the DRS chips could work happily in the normal way while if the capacitor is only 4.7nF all of them got very hot. Would you please provide some suggestions why there should be such a problem?

    Thanks a lot!

I found that sometimes even a reinitialization fails if the pull-down resistors are missing. So instead playing with capacitors at DVDD, I would just solder two resistors on the board which should fix the problem completely.

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