ISO7041: ISO7041 for Isolated I3C communicaition

Jaydip Vadodariya

Prodigy 40 points

Part Number: ISO7041

Tool/software:

Hi TI Team,

We are implementing I3C communication in one of our products and require isolated I3C.

Upon reviewing available isolation chips, we are unable to find ultra-low-power bidirectional isolators in the market.

We have one question: can we achieve isolation by shorting two reverse-direction pins, as shown in the attached diagram, to use the isolator pins bidirectionally?

8 months ago

0 Aaditya V. 8 months ago

TI__Genius 14705 points

Hi Jaydip,

The ISO7041 is a unidirectional digital isolator with CMOS style outputs. Considering this, simply shorting the 2 channels will not enable the digital isolator to work bidirectionally. Please check this document to see how digital isolators can be used for I2C applications: https://www.ti.com/lit/an/slyt403a/slyt403a.pdf. Since I2C is similar to I3C, this may be helpful for you as well.

Another option could be a bidirectional (open collector) isolators like ISO1640. This device could be a possible option for your application, but is limited to I2C data-rates.

Let me know if you have further questions.

Regards,
Aaditya Vittal

0 Jaydip Vadodariya 8 months ago in reply to Aaditya V.

Prodigy 40 points

Hi Aaditya,

Thank you for clarification.

We are using the 100R resistor to short, but what happen if we use diode in place of resistors?

I went through the reference document that you have shared, reference design uses the diodes as well.

Additionally I3C is mandatory to use due to inband interrupt requirements.

Let me know your thoughts.

Thanks,

Jaydip

0 Clemens Ladisch 8 months ago in reply to Jaydip Vadodariya

Guru 304440 points

It is not possible to create a bidirectional isolator by adding resistors or diodes to an isolator with unidirectional channels.

You must use an isolator that understands how to solve conflicts for signals going in both directions (for I³C, low level has priority over high level), and currently, the only such isolators are I²C isolators.

0 Jaydip Vadodariya 8 months ago in reply to Clemens Ladisch

Prodigy 40 points

Thanks! Clemens, for providing the details.

Could you please suggest how to use this isolator as bi-directional for I3C or any other solution?

Thanks,

Jaydip

0 Aaditya V. 8 months ago in reply to Jaydip Vadodariya

TI__Genius 14705 points

Hi Jaydip,

In order to use a digital isolator with I2C, it is not as simple as using diodes to connect 2 channels together.

As mentioned in this document Designing an Isolated I2C Bus interface by using digital isolators (Rev. A) (ti.com), there are several components that are required such as a resistor network, transistors, and diodes. I would highly recommend following the design recommendations highlighted in this document to use I2C/I3C with a digital isolator.

An additional potentially useful document I recommend: How to Isolate Signal and Power for I2C (Rev. B) (ti.com)

Regards,
Aaditya Vittal

Isolation

Isolation forum

ISO7041: ISO7041 for Isolated I3C communicaition