[time-nuts] PLL suggestions

[Dan Kemppainen]

Hi All,

We've got a project going on where we need a 125MHz clock that should be 
locked to 10MHz. I'm considering an on board 10MHz oscillator and 
external 10MHz input to utilize an external standard to lock the 125MHz 
which would PLL a 125MHz source.

The 125MHz becomes a reference for 3.125Ghz, as well as logic running at 
125Mhz. (Currently this system is running on small 125MHz TCXO.) 
Basically we need a reasonably clean 125MHz signal, but locked to 10Mhz 
for frequency reference.

We've identified a few VCXO's that seem to be low noise and are small 
enough. The 10Mhz is easy enough. However my stumbling block is a simple 
PLL.

What I'm looking for is a simple, small PLL chip. Something with 
external analog loop filter components to allow easy tweaking would be 
preferred.

In my perfect world, this chip would be a COTS part, with pin strappable 
divider configuration or similarly simple hardware configuration. An OTP 
device would work as well, as would one with it's own memory and 
external programmer. If necessary a small PIC or similar could be used 
to configure the PLL, but that's one chip which would be nice to avoid.

Smaller compact package SMT parts are fine. This is going on a board 
with lots of SMT components, leadless flat pack devices and BGA's, so 
smaller is better.

If any of you have any suggestions, I'd appreciate it.

Happy new year!
Dan