all PPS inputs are 50-Ohm-terminated; you can s
And, as Marcus Leech said, 2.52V should probably be OK – If you go
to the datasheet that he linked to, p.8, you'll see that for the
used Vcc of 3.3V, the rising edge threshold voltage is less then
1.16V; which means that over the 1.2K/2K voltage divider (R590 /
R592) a total voltage of a little less than 3/2 * 1.16V = 1.74V
must exist. Your 2.52V is higher than that. You should be fine,
though not by a huge amount.
On 05.05.2016 14:28, khalid.el-darymli
I will appreciate it if someone could please answer my
The PPS signal output from the FireFly 1-A GPS is
designed to drive a high impedance load (not 50 ohms).
Without 50 ohm terminator, my scope placed at the output
of our PPS fan-out reads 3.68 V (as shown in the
attachment). With 50 ohm terminator, my scope reads 2.52
Now our fan-out circuit is designed to be a high input
impedance and a 50 ohm output impedance. What is the input
impedance for the PPS receiver on the N200 unit?
I understand that the PSS input for N200 is recommended to
be in the range [3.3 V, 5 V],
Maybe due to impedance mismatch, the actual input PPS voltage
taken from our fan-out to the N200 unit exceeds the 5V thus
causing stability issues inside the N200 unit. I am just
guessing because using the same set-up, same code, everything
worked before just fine. The only major change we made was in
our fan-out unit.
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