ISO6763: Could ISO6763 be used in I2C isolation

Terry Wang

Part Number: ISO6763
Other Parts Discussed in Thread: ISO1640, TPS23861EVM-612

Tool/software:

Hi,

I would like to use a ISO6763 in bidirectional I2C isolator.

I connected two unidirectional channel on digital isolator and added a buffer IC for separating in/out of I2C_SDA as below figure.

Could I use this circuit to achieve a bidirectional channel for I2C communication?

Thanks.

Terry

2 months ago

0 Clemens Ladisch 2 months ago

Guru 285040 points

No, this does not work. I²C uses open-drain signals, and an I²C buffer must ensure that a low input is not looped back to the output on the same side.

You should use an I²C isolator like the ISO1640.

0 Terry Wang 2 months ago in reply to Clemens Ladisch

Prodigy 10 points

Hi
We referred the EVM User's guide of TPS23861 as below.

It used a ISO7261CDW (U2) and a buffer for I2C isolator on page 26 (Figure 24. TPS23861EVM-612 (Motherboard) Schematic: Control).

https://www.ti.com/lit/ug/sluuay8e/sluuay8e.pdf?ts=1730183531475&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTPS23861

That's why I would like to use ISO6763 for I2C communication.

Could you help check this design again?

Thanks

Terry

0 Aaditya V. 2 months ago in reply to Terry Wang

TI__Genius 12035 points

Hi Terry,

Using digital isolator for I2C communication requires a more involved circuit around the isolator itself in order to achieve bidirectionality. So not only would a buffer was used in the document you provided, but they also had several other components, such as FETs, to allow for bidirectional I2C communication. For more information on using digital isolators for I2C communication, Please check this document: Designing an Isolated I2C Bus interface by using digital isolators (Rev. A)

As Clemens said, the ISO1640 could also be a great option since this device is designed for I2C communication. Therefore, there is no need for added complexity and circuitry for your system. Please find more information regarding this device at the product page: ISO1640 data sheet, product information and support | TI.com

Regards,
Aaditya Vittal

0 Terry Wang 2 months ago in reply to Aaditya V.

Prodigy 10 points

Hi Additya,

We want to cost reduction, so I designed an unidirectional isolator(ISO6763) for I2C communication.

I added several components for designing a isolated I2C bus interface by using digital isolators after referring this document.

Could you help check this design again?

Thanks

Terry

0 Clemens Ladisch 2 months ago in reply to Terry Wang

Guru 285040 points

The TPS23681 has separate pins for SDA input and output, and never uses clock stretching, so it is actually possible to use it with a digital isolator as shown. The SDA output (I2C_OUTD) must go through an open-drain buffer; your circuit in the question did not show this.

Preventing a loopback on one side is enough, and the TPS23681 already does this. You can use I2C_SDA directly.

0 Terry Wang 2 months ago in reply to Clemens Ladisch

Prodigy 10 points

Hi Clemens,

Sorry for the confusion.

Yes, the PSE IC has separate pin for SDA input and output. ( 3 wire I2C bus, SCL, SDA IN, SDA OUT)

But It is 2 wire I2C bus on our system. ( 2 wire I2C bus, SCL, SDA)

I modified the schematic for using an open-drain buffer as below.

Could you help check this design?

Thanks.

Terry

+1 Andrew J 2 months ago in reply to Terry Wang

TI__Mastermind 22435 points

Hello Terry,

The following solution looks like it would work. Please test and let me know if you have any more questions.

Best,
Andrew

Isolation

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ISO6763: Could ISO6763 be used in I2C isolation