Power supply of Tobi/OveroWater boards

[OliverMarc]

Hi,

I have a question concerning the power supply of an overo water together
with the Tobi expansion board.

I need to power both boards with an unregulated dc input voltage of
5-18V, therefore (afaik) I cannot get stable 5V to power the barrel
connector. After looking at the schematics it seems like one option
would be to directly attach 3.3V (SV1 Pin2), which is connected to
VSYSTEM and should power the COM module without problems. The only part
that needs 5V seems to be the USB interface. I could live without USB,
so might this solution help or am I missing something?

Any help would be greatly appreciated.

Thanks,
Oliver

--
Oliver Mischke

escrypt GmbH - Embedded Security
Lise-Meitner-Allee 4
D-44801 Bochum, Germany

phone: +49 (0)234 / 43 87 02 31
email: omischke@...
web: www.escrypt.com

Geschäftsführer: Dipl.-Psych. Katrin Mannheims MBA, Dr.-Ing. Jan Pelzl, Dr.-Ing. Thomas Wollinger
Handelsregister: Amtsgericht Bochum Nr. 7877 - St.-Nr. 350/5714/0765
Sparkasse Krefeld - Konto 12 039 - BLZ 320 500 00



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[Bruce Bernstein]

Another possibility might be to swap out C42 and C43 for higher voltage
caps if you can keep your unregulated source down to 16V max.  The
TPS6111 on the Tobi is rated for the higher voltage.  I don't understand
why they used smaller caps and restricted the voltage.
Bruce


Oliver Mischke wrote:

> Hi,
>
> I have a question concerning the power supply of an overo water together
> with the Tobi expansion board.
>
> I need to power both boards with an unregulated dc input voltage of
> 5-18V, therefore (afaik) I cannot get stable 5V to power the barrel
> connector. After looking at the schematics it seems like one option
> would be to directly attach 3.3V (SV1 Pin2), which is connected to
> VSYSTEM and should power the COM module without problems. The only part
> that needs 5V seems to be the USB interface. I could live without USB,
> so might this solution help or am I missing something?
>
> Any help would be greatly appreciated.
>
> Thanks,
> Oliver
>
>  

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[OliverMarc]

The problem is that the input voltage is also connected to a
"power-distribution-switch" (TPS2041) that is only rated up to 5.5V
which then powers a signal called usb_vbus which is also connected to
the overo water module (J1-31).
Since the TPS62111 is rated from 3.8-17V and the TPS2041 has an
operating range from 3.7 to 5.5.V we could get stabilized 4V out of the
5-18V Input Range and power the barrel connector with that voltage.
Unfortunately, since the schematics of the overo water are not public,
we do not know how the usb_vbus voltage is used on the overo board, e.g.
if it really needs 5V or not.
The manuals are somehow contradicting. On the one hand side it says only
use 5V regulated DC, on the other hand the Toby Board is rated for
4-5.5V input voltage.
Does anybody know if 4V would be sufficient?

Many thanks,
Oliver

Bruce Bernstein schrieb:

> Another possibility might be to swap out C42 and C43 for higher voltage
> caps if you can keep your unregulated source down to 16V max.  The
> TPS6111 on the Tobi is rated for the higher voltage.  I don't understand
> why they used smaller caps and restricted the voltage.
> Bruce
>
>
> Oliver Mischke wrote:
>  
>> Hi,
>>
>> I have a question concerning the power supply of an overo water together
>> with the Tobi expansion board.
>>
>> I need to power both boards with an unregulated dc input voltage of
>> 5-18V, therefore (afaik) I cannot get stable 5V to power the barrel
>> connector. After looking at the schematics it seems like one option
>> would be to directly attach 3.3V (SV1 Pin2), which is connected to
>> VSYSTEM and should power the COM module without problems. The only part
>> that needs 5V seems to be the USB interface. I could live without USB,
>> so might this solution help or am I missing something?
>>
>> Any help would be greatly appreciated.
>>
>> Thanks,
>> Oliver
>>
>>  
>>    
>
>
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> _______________________________________________
> gumstix-users mailing list
> gumstix-users@...
> https://lists.sourceforge.net/lists/listinfo/gumstix-users
>  

--
Oliver Mischke

escrypt GmbH - Embedded Security
Lise-Meitner-Allee 4
D-44801 Bochum, Germany

phone: +49 (0)234 / 43 87 02 31
email: omischke@...
web: www.escrypt.com

Geschäftsführer: Dipl.-Psych. Katrin Mannheims MBA, Dr.-Ing. Jan Pelzl, Dr.-Ing. Thomas Wollinger
Handelsregister: Amtsgericht Bochum Nr. 7877 - St.-Nr. 350/5714/0765
Sparkasse Krefeld - Konto 12 039 - BLZ 320 500 00



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