Microchip Technology GPS-2700, Руководство пользователя

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GPSCon Utility

2020 Microchip Technology Inc. DS50003016A-page 75
visible over 200 hours. On the left side of the screen the EFC range over this 200 hour
plot is displayed vertically as 6.7E-11. This means the drift of the EFC value due to
aging is ~2.9E-09 per year.
This is the same as 0.008
ppb drift due to aging per day.This crystal aging is fully
compensated by the firmware with and without GNSS reception of course.
The board temperature is shown in green. We can see it ranges from 37.17°C to
41.17°C. The CSAC senses the temperature change and actively compensate for the
change.
In
Figure 5-9 , which is a zoom of Figure 5-8 , we can see the phase offset error of the
CSAC to the UTC GNSS reference. We can see the maximum drift is -8.17ns to
+8.68
ns. The average is (TI av = –0.12 ns). The standard deviation over the 200 hour
plot is sd = 2.25 ns. This means the average error of the 10 MHz phase of this unit over
200 hours is only ±2.25 ns
RMS
. Or, in other words the average jitter (wander) over 200
hours of operation is:
EQUATION 5-1:
2.25ns 200 hours

3600

3.13 10
15 –

=
The unit disciplines its internal 10 MHz reference to within less than ±9 ns peak to peak
of UTC at all times, which is less than one complete clock cycle at 10 MHz.