[time-nuts] Buffering a PPS signal

[Bob Camp]

Hi

Parallel up as many inverters (or logic buffers) as you feel you need. Much less delay than the MOSFET drivers. Small packages for easy layout. Run off of 5 volts (or what ever…). Put a resistor in series with the output of each of them and they will equalize very well. 

Bob

On May 17, 2012, at 7:35 PM, Michael Tharp wrote:

> Greetings,
> 
> As I mentioned briefly a few days ago I'm working on an interface board for the Trimble Resolution SMT carrier board to provide a convenient way to get power in and PPS/serial out. The PPS output is a 3.3v, 125 microsecond long pulse and I'd like to buffer it with something that can drive a 50 ohm terminated line. What's the best way to go about doing this? I've looked at using a MOSFET driver like FAN3111ESX but most of these have a moderate (30-50ns) delay with a moderate temperature coefficient, but perhaps I'm expecting too much.
> 
> For people interested in buying the board, it will have USB and RS-232 (with PPS on the Carrier Detect line) plus the 50 ohm PPS output on BNC. Physically, it's the same size and shape as the RSMT board itself and will fit directly on top. Total cost should be about 20 USD.
> 
> Current schematic is here, comments welcome:
> http://partiallystapled.com/~gxti/circuits/2012/05/17-piggyv2.png
> 
> Cheers,
> -- m. tharp
> 
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