Sierra Wireless AirPrime XA1110, Hardware Design Manual, Page: 29 / 36

Rev 3.0 Aug.19 29 41111116
E
Appendix E: How to Efficiently Transfer
1PPS Through Extended Distances
There are several aspects to note when transferring a 1PPS signal through a long
cable which will result in a 1PPS signal degradation, an increase in noise, and an
increase in signal delay. As the 1PPS signal is traveling through the communication
cable, impedance matching must be implemented to prevent waveform distortion.
Depending on your application, an OP-amp can be added to control the accuracy of
the voltage level for the 1PPS signal.
When using a 1PPS signal for time synchronization, the OP-amp chosen should have
a high slew rate property to prevent a large delay in the 1PPS. The accuracy level of
1PPS for Sierra Wireless GNSS modules is within 100ns. This applies to most of
Sierra Wireless’ MTK GNSS modules. The reference design in
Figure E-1 below can
be used to improve accuracy to within 80ns.
Figure E-1: Design to Improve Accuracy to within 80ns