[time-nuts] dsPICs and GPSDOs

[Bob Stewart]

Once I got my TIC going, I suppose it was inevitable that I build a GPSDO with a dsPIC33.  I have a few dsPIC specific questions for anyone who designs with them.

1. VCAP.  The datasheet says that it should be a surface mount device.  I had hoped to avoid those.  Can I get away with a 10uf tantalum placed at  .1" from the pin?  I'm using a 28-pin DIP dsPIC, which will probably be socketed.


2. The datasheet suggests an inductor between AVDD and VDD.  Given that I'll only be reading the ADC twice a second (PPS and temps), can I just use the straight wire that I have already penned in?  I'm starting to run out of board space.

As to why I'm using a dsPIC: the one I chose has a number of features that suit me, such as 2 UARTs, SPI, buffered ADC, (audio) DAC, and especially relocatable pins.  To be honest, I don't know whether this will result in a general purpose GPSDO engine (with sawtooth correction) or a smoke machine, but I'm hoping for the best.  I'll try to resist the temptation to make more posts until I have a completed project.

Bob - AE6RV