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reel
2 posts
Popping In
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15-05-2008 06:17
Looking at the circuit diagram for DigiButler in April's edition (and at that found on the Freescale site) I see that both VDD1 (pin 74) and VDD2 (pin 45) are connected to the +3V3 rail. Reading the reference manual for the MCF52235 (Rev 5) it says on p2-7 (footnote 5) "The VDD1, VDD2, VDDPLL and PHY_VDD pins are for decoupling only, and should NOT have power directly applied to them." Then on p2-15 it repeats this with the added note "Do not connect power supply voltage directly to these pins unless the desire is to send the device into a slow but certain death spiral."
My question is should we be concerned about this? Is it really an issue? Am I misreading the manual? Are the schematics out of date and the released PCB addresses this issue?
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Jojo l'astico
1 post
Popping In
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24-05-2008 18:02
Hello,
I wondered if VDD pins goes to the positive rail of the supply too. On the evaluation board of MCF51235 made by freescale, VDD pins are not connected to the positive rail supply voltage, while VDDX pins are connected to the supply.
I will really apreciate if someone tell about his experience with digibutler, particularly about this subject.
What about the board elektor sells ?
Thank you very much for your help.
Joel
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Elektor Editor
468 posts
Power User
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03-06-2008 09:05
The issue with the two pins has been confirmed and we are developing a workaround and/or a new board design.
Our apologies, also on behalf of Freescale who designed the board.
Jan
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reel
2 posts
Popping In
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03-06-2008 13:42
Thanks for clarifying this. I wanted to be clear on the issue so that any future boards I design based on these coldfire chips will have the best chance of success. I hope you are able to get the workaround done easily so people aren't disappointed with the boards.
Leon
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