[time-nuts] Buffering a PPS signal
Michael Tharp
gxti at partiallystapled.com
Thu May 17 23:35:24 UTC 2012
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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