New Errata Document: Issue on I2C buses.

We would highly recommend following the recommendations outlined in the errata.  This includes adding the termination resistors..  We are working on a device revision that would remove this requirement but It would be in your best interest to add those resistors and then DNI when the new version becomes available.

Hi,

Similar issue with our customer.
They have already designed their custom boards without the
"series termination resistors" on SCL & SDA terminals.

As their mass production starts in few days, adding the
"series termination resistors" may require redesigning the custom board,
which may cost time and money.

But we are worried about the effect of this erratta as it mentions
"potentially increases power supply noise"
could you please let us know what amount of impact it may cause on the power supply?
and will it be risky to continue without the series termination?

Please let us know if there is any other ways to overcome the issue
without the additional hardware(series resistors).

Best Regards.
Paddu

This is not an easy question to answer.  The effect on power supply noise depends on may variables like the power source, power distribution network, susceptibility of various components, etc.

The other concern is signal ringing.  The effect of signal ringing also varies from system to system.

Therefore, the Advisory recommends the series termination resistors to limit the current and damp any signal ringing.

Many systems were built using AM335x without any reports of problems related to this I2C issue.  The issue was recently found when a system that had multiple I2C devices connected via long signal paths had an issue with excessive signal ringing.

Regards,
Paul

Hi Peaves,

Thank you so much for the quick response,
with all the comments we assume that it is uncertain or it is little bit risky
proceeding without the series termination.
And it may require thorough investigation on the various components of the
custom board to find out the effect on power supply noise.

Unfortunately,it seems the customer cannot afford to install the
additional termination resistors bcos of their time constraint.

I believe there is no other way,
but just in case please let us know if there are any other possibilities
like software workaround.

Best Regards.
Paddu

No, there is not another workaround.   If there had been another workaround option, it would have been published in Advisory 1.0.26.

We are working on a device revision that would remove this requirement.  Adding the resistors will lower any risk of the issue causing a problem until the new silicon revision becomes available.

Regards,
Paul

It's really a shame since we sent our design to fabrication few days before there was published the errata. I hope there won't be problems with the communication with the PMIC and at least be able to evaluate the prototypes...

Regards,

Manuel.