DS90UH947-Q1: OLDI Frequency Counter

Jared Becker

Part Number: DS90UH947-Q1

Hi Team,

I would like to clarify the description for register 0x5F in the 947 datasheet. In the second to last sentence, it says "A value of 0 indicates that OLDI receiver is not detecting a valid signal". Then in the last sentence, it says "When the OpenLDI input is suddenly removed, this register will retain its value".

What is the quantification for "suddenly removed"? If OLDI is removed, are there times where you would see a value of 0 and other times where the OLDI frequency value would remain? Under what circumstances would you see the value retained vs a value of 0.

Thank you,

Jared

over 6 years ago

0 Casey McCrea over 6 years ago

TI__Guru** 103215 points

Hello Jared,

I believe this is referring to the fact that the OLDI frequency register has a fixed update rate so when you remove the clock there will be a short time before this register updates as we have discussed in our other thread. But we can do a spot check on this too to see behavior. It may take a day or two.

Best Regards,

Casey

0 Jared Becker over 6 years ago in reply to Casey McCrea

TI__Genius 11845 points

Hi Casey,

Thanks for the note! Have you had a chance to verify that behavior?

Best,

Jared

0 Casey McCrea over 6 years ago in reply to Jared Becker

TI__Guru** 103215 points

Hey Jared,

We will need a few days to spot check it. We should be able to respond back early next week.

Best Regards,

Casey

0 Casey McCrea over 6 years ago in reply to Casey McCrea

TI__Guru** 103215 points

Hello Jared,

Since we have had some offline conversation about this I will post the findings here:

The OLDI frequency detect circuit is very sensitive to noise so for systems where there may be some external noise, the clock detect bit may go high occasionally if the OLDI is disconnected or static. The FREQ_STBL bit may be a better choice for checking for a valid clock detected, and it also has programmable stable time thresholds too.

Best Regards,

Casey

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DS90UH947-Q1: OLDI Frequency Counter