Accuracy of TMS320F28027 internal clock?

I am not sure about the accuracy either but the internal clock is accurate enough for robust serial communication in a electrically noisy environment. We have systems utilizing a member of this device for RS485 communication between user interface and multiple drives (>150HP, 690V) . Would you please share what kind of accuracy you are looking for and why?

Production devices will have an accuracy of 10MHz +/- 3% max over S rated devices(-40C to 125C).

Best,

Matthew

Sorry about the late reply.

Actually I think I need accuracy only available from crystals. It's for data collection and digital filtering.

The reason I asked is that nowadays I get surprised both by how good things are and how bad things are and TI didn't specify it so I didn't really know what to expect.

Mathew's answer was pretty much what I expected though.

/Janne

Janne,

Starting with TMS qualified material we will support a oscillator calibration function that should give 10MHz +/-1% over the full temperature of the device.  The function calls/examples are available for review in the latest version of the header file examples; under the osc_comp example

http://focus.ti.com/docs/toolsw/folders/print/sprc832.html

Note this is only applicable to TMS silicon; as these functions were not factory programmed in TMX devices.  Not sure if this will allow you to move away from external soln or not.

Best,

Matthew

Hello Janne.

Here is a text from TMS320F2802X Data Manual : "The device can be clocked by either of the two internal zero-pin oscillators, an external oscillator, or by a crystal attached to the on-chip oscillator circuit (48-pin devices only). A PLL is provided supporting up to 12 input-clock-scaling ratios." Citation means that frequency accuracy and stability depends from which clock source are you using. If you are using crystal, then accuracy depends from crystal accuracy and stability. See at those links and you will find how accurate and stabil typical  oscillators with quartz are :http://www.vectron.com/products/xo/vcs3.pdf (quartz integrated with oscillator) and standalone crystal rezonators http://www.ecsxtal.com/store/pdf/hc49u.pdf. Those are the key parameters for your solution. As you see with such a crystal oscillators you can obtain a +/-30ppm accuracy and +/-50ppm thermal stability. The only thing which is TMS320@802X dependent in such a case is PLL loop quality. Note that peripheral devices almost ever use divided PLL frequency so some phase shifting doesn't matter.

Lucas

Hi Jeffrey,

Can you please create a new post for your question?  This will ensure that you get a timely response from the right people.


Thank you,
Brett