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Run CubeSat Kit with +3.3V Only?

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Run CubeSat Kit with +3.3V Only?

Postby Unregistered User » Fri Sep 19, 2008 2:23 am

Refer to the FM430 Datasheet (http://www.cubesatkit.com/docs/datasheet/DS_CSK_FM430_710-00252-C.pdf) for the information below.

1) It's imperative that the maximum voltage on the +5V (+5V_SYS) power bus be limited to +6V. Anything higher will damage the FM430. So, for a system that neither requires nor generates +5V, the +5V (+5V_SYS) signal should be left untouched by the system EPS.

2) If you need to bus your higher-than-+5V signal around, you can put it e.g. on USER6 and USER7.

3) Now that there is no +5V (+5V_SYS) signal, you need to power the FM430. The simplest way to do this is to fit the R68 resistor on the FM430 (the Dev Board has a corresponding jumper JP16). This way, VCC_SYS from the bus feeds VCC on the FM430. This _requires_ that VCC_SYS be +3.3V (only). This configuration feeds +3.3V into an unpowered regulator U5, but this is generally not an issue, because there is no path to ground from U5's input.

4) Note that without +5V (+5V_SYS), you have no power going to the MHX socket.

So, you can test all of this by fitting jumper JP16 on the Dev Board, and feeding the Dev Board with +3.3V via JP6.

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Re: Run CubeSat Kit with +3.3V Only?

Postby Unregistered User » Fri Sep 19, 2008 10:38 am

We have a question regarding the required voltage for the FM430
processor board. At present, our CubeSat absolutely requires 3.3V and a
voltage probably higher than 5V (like 7V or 9V). In other words, the
only reason for having a 5V-volt power bus would be to feed the FM430.
Therefore, we were wondering whether we could just NOT have a 5V supply
on the CubeSat and feed theFM430 directly with 3.3V. One of the FAQs
leads us to believe that this is the case:

If your CubeSat already generates a suitable VCC, you can disable and/or
disconnect the regulator on the Flight Module and feed it VCC via the
CubeSat System Bus connector.


Is it thus correct that we can just supply 3.3V to the FM430. If so, is
the procedure to do so clearly indicated in the instructions ? (I
haven't gone back to check.) If we only supply 3.3V, what
functionalities do we loose on the FM430 ? Are we then going to run into
incompatibilities with the development board ? Is it a good idea to not
have 5V ? Are there things we should be aware of if we do not provide 5V
? What is you advice ?

Thanks a lot for your reply.

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Posts: 36
Joined: Thu Aug 09, 2001 11:00 pm


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