The drive to tighter and tighter time and phase requirements shows no sign of slowing – whatever G you may be working on. Chronos is a Microchip partner and out of the box the TimeProvider 4100 (TP4100) delivers (when locked to GNSS) PRTC-B performance of 40ns to UTC. Combining a TP4100 with a caesium (like the TimeCesium) as an ePRTC lowers this to 30ns, and after weeks of conditioning will keep to within 100ns of UTC for 14 days should GNSS be lost.
Performance Considerations
There are, of course, specified performance levels to consider. That includes using multi-band GNSS. I have seen measured results of an ePRTC still delivering sub 100ns after more than two months.
However, we are now entering the sub nanosecond world. Using Optical Timing Channels, the TP4100 used as a Class D Boundary Clock is specified at 5ns of error per hop; again, the reality is far better than that, with real-life measured performance of a Microchip vPRTC based on TP4100s with optical connectivity delivering less than 1ns per hop across a 700km network!
Avoiding Temperature Issues
But if these clocks can deliver this level of performance, what do I need to worry about? Well, if you are planning for your network to live with these levels of performance, using fans for cooling boundary clocks (whether standalone or as part of a Network Element’s functionality) is simply not a design choice you can make – even devices located next to the clock with fans may affect performance.
Typically, the operation of a cooling fan in a clock can introduce a 12/15ns error; meaning at the very least that Class D performance is simply not attainable.
Summary
If you’re deploying a nanosecond timing system as part of your timing setup, then there’s plenty of potential issues that can cause degradation in its timing integrity. Even a fan can become your enemy. For the sake of performance and future proofing, I would advise that you make sure you are deploying devices that do not require fans for their heat management.
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