Re: Consistency of DCO parameters across multiple samples of a given part number?
"Onestone
[email protected] [msp430]" <
[email protected]>
Thu, 21 Jun 2018 12:59:33 +0930
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The accuracy and repeatability of the DCO clock for the pre-programmed
values is around 3%. I tested just 20 samples and found that typically
this was closer to 1%. Certainly on a range of 200 shipped units, using
a calibrated DCO for a 460kb UART, no complaints were received regarding
failed communication to a PC based program. But this is a small sample.
For any other value of DCO frequency I would expect much worse, given
that Ti rate some of their calibrated values as worst case +/-6% over
the full temperature range. What prevents you from using one of the
calibrated frequencies, or even a cheap watch crystal. Not all, but
most, of my designs use a watch crystal, and still achieve very low mean
power consumption, and I design very tiny systems typically 1cm square
or smaller, so size shouldn't be an issue.
Al
On 21/06/2018 9:01 AM, David Feldman [email protected] [msp430] wrote:
> I am working on a project that uses MSP430G2452IPW14 (14 pin TSSOP package.)
>
> At initialization, I set MCLK and SMCLK sourced from DCO and set DCO to my chosen clock frequency (I did not rely on Info flash segment D calibration parameters, as those didn't yield the frequency I require.)
>
> I was surprised to find upon building my second prototype of the project that the DCO frequency, using the same parameters as the first prototype, was off considerably (perhaps 5% or so.)
>
> What should I expect in terms of DCO frequency consistency? Should I plan a calibration step for each device I use (i.e., find it's correct parameters to obtain the required frequency?) I do not have a crystal or other primary frequency source in the design -- the DCO is being used stand-alone with no discipline mechanism available.
>
> Thanks,
>
> Dave
> [email protected]
>
>
> ------------------------------------
> Posted by: David Feldman <[email protected]>
> ------------------------------------
>
> To unsubscribe from the msp430 group, send an email to:
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<font size="-1">The accuracy and repeatability of the DCO clock for
the pre-programmed values is around 3%. I tested just 20 samples
and found that typically this was closer to 1%. Certainly on a
range of 200 shipped units, using a calibrated DCO for a 460kb
UART, no complaints were received regarding failed communication
to a PC based program. But this is a small sample. For any other
value of DCO frequency I would expect much worse, given that Ti
rate some of their calibrated values as worst case +/-6% over the
full temperature range. What prevents you from using one of the
calibrated frequencies, or even a cheap watch crystal. Not all,
but most, of my designs use a watch crystal, and still achieve
very low mean power consumption, and I design very tiny systems
typically 1cm square or smaller, so size shouldn't be an issue.<br>
<br>
Al<br>
<br>
</font><br>
<div class="moz-cite-prefix">On 21/06/2018 9:01 AM, David Feldman
<a class="moz-txt-link-abbreviated" href="mailto:[email protected]">[email protected]</a> [msp430] wrote:<br>
</div>
<blockquote type="cite"
cite="mid:[email protected]">
<pre wrap="">I am working on a project that uses MSP430G2452IPW14 (14 pin TSSOP package.)
At initialization, I set MCLK and SMCLK sourced from DCO and set DCO to my chosen clock frequency (I did not rely on Info flash segment D calibration parameters, as those didn't yield the frequency I require.)
I was surprised to find upon building my second prototype of the project that the DCO frequency, using the same parameters as the first prototype, was off considerably (perhaps 5% or so.)
What should I expect in terms of DCO frequency consistency? Should I plan a calibration step for each device I use (i.e., find it's correct parameters to obtain the required frequency?) I do not have a crystal or other primary frequency source in the design -- the DCO is being used stand-alone with no discipline mechanism available.
Thanks,
Dave
<a class="moz-txt-link-abbreviated" href="mailto:[email protected]">[email protected]</a>
------------------------------------
Posted by: David Feldman <a class="moz-txt-link-rfc2396E" href="mailto:[email protected]"><[email protected]></a>
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