[ntp:questions] Performance?

David J Taylor david-taylor at blueyonder.neither-this-part.nor-this-bit.co.uk
Wed Dec 31 06:55:27 UTC 2008


Unruh wrote:
[]
> OK, I will believe you. However since the driving voltage of the
> garmin 18 is usually taken from the USB and is 5 V, the output PPS
> voltage will be less than 5V. ( maybe 4.5) Does that make a
> difference?

In my experience, no.  Anything above about 3V should be OK.

Taking an example at random, the LT1780/LT1871

  http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1007,C1016,P1654

  http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1007,C1016,P1654,D2520

the thresholds are given as:

  Low: 0.8V (minimum) 1.3V (typical)
  High:  1.7V (typ), 2.4V (maximum)
  Hysteresis: 0.1V (min), 0.4V (typ), 1.0V (max)

Cheers,
David 




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