TMS320F280049: Errata - I2C Series Termination

Joakim

Intellectual 1940 points

I am writing in regards to the following errata item for the TMS320F28004x microcontroller:

The suggested workaround for this item is to place series termination for both SCL and SDA at the MCU. Is there a recommendation for the value of the series element? My research has found a range of 50R to 300R in separate datasheets and applications manuals discussing series termination for I2C.

Thanks in advance for your help.

Joakim

over 3 years ago

0 Manoj Santha Mohan over 3 years ago

TI__Guru 55700 points

Joakim,

Choice of Series termination resistor depends upon both bus speed (baud rate), bus capacitance and pull-up resistor used. In general, higher bus capacitance requires lower value pull-up resistors and lower pull-up resistor needs a smaller series termination resistor.

For example, For a bus capacitor of 50pF and baud rate = 400 KHz, you have to choose pull-up resistor lesser than 7 K ohm and series resistor of at-least 20 ohms.

What is the bus capacitance and pull-up resistor used?

Regards,

Manoj

0 Joakim over 3 years ago in reply to Manoj Santha Mohan

TI__Intellectual 1940 points

Hi Manoj!

Thanks for the quick response. We plan to run this bus at 400kHz (fast mode), with 2.2k-ohm pull-up resistors, and we have an estimated bus capacitance of 34pF.

0 Manoj Santha Mohan over 3 years ago in reply to Joakim

TI__Guru 55700 points

It is good that you have stronger pull-up of 2.2K ohm. With a bus capacitance of 34 pF, you should be good with series resistor of 50 ohms. for fast mode.

0 Joakim over 3 years ago in reply to Manoj Santha Mohan

TI__Intellectual 1940 points

Thanks a lot Manoj !

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TMS320F280049: Errata - I2C Series Termination