Chris R. Anderson wrote:
Voltage-wise be aware that the Cyclone III part needs a 1.2V VCCint
and VCCDpll, in addition to the VCCIO which will need to be 1.8V on
the Beagle side and 3.3V on the ADC/DAC side which you've already
noted. There's also the 2.5V VCCA for the FPGA's internal PLL. Be
prepared for VCCint to draw up to several amps too - depends on the
internal speed and utilization.
Drat and blast, you had to remind me of that :-). This is what happens
when you spend all day teaching Engineering to English majors. I guess
that probably means we'll need to use at least one switching regulator.
I've had good luck and experience using the LT1765. It's good up to 3A
and should be useable down to 1.2V.
TI actually makes a family of dual-output LDOs that can source up to 2A:
http://focus.ti.com/docs/prod/folders/print/tps70351.html
So you can have your linear regulator and high current too.
It looks like we're going to go with the AD9860/9862, and design the
board so that either one can be installed.
Those seem nice - lots of goodies inside and they'll help maintain
compatibility with existing USRP applications. Kinda old and expensive
though - using a simpler/cheaper device with just a converter and
doing the signal processing in the FPGA might be more cost effective.
I agree, they're expensive and a few years old, but we can make use of a
lot of existing code. Tell you what, let's get this board to work, and
then see if we can find a better/faster/cheaper way to do it for REV 2.
Sounds like a plan. I took a look at a few alternatives yesterday and
while there are a fair number of them out there, (ADI, Maxim, etc), most
are provided in QFN/CSP packages that are just a step up from BGAs.
The 9860/9862 at least come in flatpacks that a human can solder. The
only real alternatives are to go to straight ADC/DAC parts which would
probably require more distinct devices and wouldn't save $$.
More info on AIS: http://www.navcen.uscg.gov/enav/ais/default.htm
more info on DSC: http://www.navcen.uscg.gov/MARCOMMS/gmdss/dsc.htm
Pretty neat. Sounds like a great application for SDR in a tiny package.
Eric
