OsmoSDR Hardware Design Questions

Harald Welte laforge at gnumonks.org
Tue Jul 10 17:26:10 UTC 2012

Hi Christian,

On Tue, Jul 10, 2012 at 07:04:35PM +0200, Christian Daniel -- maintech GmbH wrote:
> We violate the 100mA limit by a small amount. FPGA and E4K can be
> switched off and the ADC doesn't consume much when no clock is
> applied. I don't see a problem here - at least after we fixed the
> power sequence to stop it from using the full 400mA directly on power
> up. Also a diode for external power supply is on the board. But yes -
> it will not be USB certified. But so far this is not a real-world problem.

Actually, now that you're doing a re-design for the SSC -> EBI change,
it might be an idea to make the oscillator power supply switchable and
controlled by a GPIO from the SAM3U or FPGA.  At that point, there's no
problem booting at < 100mA.

I wouldn't expect a small low-Rds_on mosefet switch to cause any problem
for the oscillator, especially since it's constant current/power...

- Harald Welte <laforge at gnumonks.org>           http://laforge.gnumonks.org/
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