[time-nuts] Frequency divider design critique request

David Forbes dforbes at dakotacom.net
Fri Jul 11 20:38:37 UTC 2008


Jim Lux wrote:
> At 10:41 AM 7/11/2008, David C. Partridge wrote:
>> M
>> All,
>>
>> CPLD - wassat?  OK, OK I have some idea, but that's about all I know.
>> Anyway these are probably BGA stuff which I couldn't hope to hand solder
>> anyway - it's enough of a stretch for me to think of hand soldering this SMT
>> board.
> 
> CPLD -> small programmable logic device (think like a PAL, but 
> bigger).. not BGAs, typically.  Anywhere from a dozen to a couple 
> hundred gate equivalents.  Some are really, really fast (e.g. 1 ns 
> prop delays, etc.)
>

I agree that a CPLD would be an excellent way to make a 10 MHz frequency divider 
board.

The Coolrunner series from Xilinx is available in 44 pin quad flat packs that I 
have no trouble soldering into place with a regular old soldering iron and some 
liquid flux. It's easy to solder SMT parts if you have a microscope and the 
right supplies.

The only problem is that the CPLD is programmable. Of course, that's also its 
strength, until it needs to be reprogrammed and you've lost the programming 
cable or the source code or the Xilinx tools fail to run on your latest PC or...






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