What is the internal RTC accuracy specified to on the Colibri T30?

Technical Support
, ,
1

What is the internal RTC accuracy specified to on the Colibri T30?

i.e. when using RTCSync protocol 6 in WinCE.

2

The RTCSync Tool is used to synchronize the time between an external Real Time Clock (RTC) and your module. The external RTC is part of your carrier board, so also the accuracy of this RTC depends on the device and the oscilator you have build on your own carrier board.

The Colibri T30 also has a clock chip on board which gets synchronize periodically by the external RTC. It has a lower precision then the external clock.

Please let us know if you need more details.

3

Hi,
Thanks for the response.

We do not have an external RTC on our carrier board, we are using the “Internal RTC of PMU on Colibri/Apalis T30”; i.e. this is what is described on your website for “RTCSync Protocol 6”.

What I would like to know, is what is the accuracy (in terms of seconds per day if possible), of that configuration using the Internal RTC on the PMU only.

Thanks,

Kevin

4

The oscillator used by the Colibri T30 module’s RTC’s is spec’d with a frequency tolerance of +/- 20ppm @25°C. It’s subject to additional frequency drift at increased temperature given by this equation: -0.035 * (T - 25)² +/-10%. (T is °C; result is ppm)

We’ve measured 35ppm RTC drift on a Colibri T30 module. Although we didn’t measure the temperature of the oscillator during this test, it was most certainly well above 25°C.

5

Hi,

Just to clarify (sorry), when you quote -0.035 * (T - 25) +/-10%, does this give the drift in ppm.

i.e. for a a temperature of 55 degrees (say), this would give an additional drift of -1.05ppm (+/-10%).

… or have I misunderstood?

Thanks

6

I apologize, I mistakenly left off that (T-25) is squared: (T - 25)². The -0.035 factor is in ppm/°C² units. Therefore, the result is in ppm. I’ve corrected my original answer.

At 55°C, the oscillator’s frequency tolerance = +/- 20ppm - (31.5ppm +/- 10%)

7

Thanks, Kevin.