DS90UB914A-Q1: Dispersion histogram of internal oscillator

Kuramochi Tadahiko

Guru 28715 points

Part Number: DS90UB914A-Q1

Hi,

Could you show me the actual dispersion of internal oscillator(nominal 20MHz) for our reference?

My customer worries that communication speed become slow by lower frequency.

Best Regards,

Kuramochi

over 7 years ago

0 Palaniappan Manickam over 7 years ago

TI__Genius 10475 points

Kuramochi-san,
The typical variation of the internal 20MHz clock is +/- 30%. The minimum SCL high time is with the max freq of the internal clock of 26MHz.

0 Kuramochi Tadahiko over 7 years ago in reply to Palaniappan Manickam

Guru 28715 points

Palaniappan-san,

Thank you for your answer!

Could you show the histogram or standard deviation of internal clock if you have the data?

Best Regards,
Kuramochi

0 Kuramochi Tadahiko over 7 years ago in reply to Kuramochi Tadahiko

Guru 28715 points

Palaniappan-san,

How is this situation?
Best Regards,

Kuramochi

0 Palaniappan Manickam over 7 years ago in reply to Kuramochi Tadahiko

TI__Genius 10475 points

The distribution should be contained within +/-30% as that is the typical internal clock variation. We do not have any histogram or standard deviation to provide.

0 Kuramochi Tadahiko over 7 years ago in reply to Palaniappan Manickam

Guru 28715 points

Palaniappan-san,

My customer requests to measure a histogram or standard deviation.
Is it possible?
I'm understanding that this is tough request.

Best Regards,
Kuramochi

0 Palaniappan Manickam over 7 years ago in reply to Kuramochi Tadahiko

TI__Genius 10475 points

Kuramochi-san,
The distribution I mentioned of +/-30% is what we have and that should be sufficient information. The nominal freq is 20MHz, so the default SCL high time is set for the max possible 20MHz+30% of 26MHz .
If the customer concern is not to exceed at the lower frequency, it would be safer to set the I2C speed to 70% of the freq. For eg if you did not want to exceed 400kHz, freq would be set for 0.7*400 = 280kHz and you would set the SCL high time and low time accordingly.

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DS90UB914A-Q1: Dispersion histogram of internal oscillator