ISO154X two battery I2C isolation

carlos.ramos14

I am designing a Smart Battery fuel gauge and I was wondering if the following is possible with the ISO154X:

I have two cells inside the Smart battery pack, with two I2C ports referenced to two grounds depicted in the picture. I want to use both I2C ports but since the signals are referenced to different grounds I can't read the two ports. Can I use the ISO154X to dereference the I2C port referenced to the middle ground? If not, can somebody suggest any other alternative on how to do this?

Thanks,

Carlos

over 8 years ago

0 Koteshwar Rao over 8 years ago

TI__Mastermind 49445 points

Hi Carlos,

Yes, you can use ISO154x for this. Isolators can be used to connect two systems with different GND references. Please make sure the potential difference between both the GND points doesn't exceed working voltage of the device (566Vpk for ISO154x).

Could you share the picture that you are referring to in your post?

Best Regards,
Koteshwar Rao

0 carlos.ramos14 over 8 years ago in reply to Koteshwar Rao

Prodigy 200 points

Thanks for the reply Koteshwar,

Please reference the schematic in page 4 of this pdf ("https://www.ultralifecorporation.com/PrivateDocuments/WP_SMBus.pdf

0 Koteshwar Rao over 8 years ago in reply to carlos.ramos14

TI__Mastermind 49445 points

Hi Carlos,

Thank you for sharing the battery connection diagram. The battery is 10V-16.8V, hence the potential difference between GNDA and GNDB would only be 16.8V max. It is safe to use ISO154x.
Please make sure Battery A is powering one side of ISO154x after down conversion to 3.3Vor 5V (like BATA5V to VCC1 & GNDA to GND1) and Battery B is powering the other side after down conversion to 3.3Vor 5V (like BATB5V to VCC2 & GNDB to GND2).

Best Regards,
Koteshwar Rao

0 carlos.ramos14 over 8 years ago in reply to Koteshwar Rao

Prodigy 200 points

Thanks again for the prompt reply,

I don't know what happened with my last post but it was incomplete. The second question I asked in the post was: Is this component made for hot swap applications? Can I disconnect and connect batteries in a hot swapping way?

Thanks,

Carlos

0 Koteshwar Rao over 8 years ago in reply to carlos.ramos14

TI__Mastermind 49445 points

Hi Carlos,

I do not think we have any hot-swap protection implemented in ISO154x at power pins. Since the bypass cap required for VCC is generally 0.1µF, I do not think hot-swapping can be an issue here. You can probably test and observe results before finalizing on schematic. Thank you.

Best Regards,
Koteshwar Rao

0 carlos.ramos14 over 8 years ago in reply to Koteshwar Rao

Prodigy 200 points

Thanks for the reply,

What I can extract from what you said is that I can use the component for battery hot swapping, but I have to be careful because there is no protection for hot swapping, right?

Thanks,

Carlos

0 Koteshwar Rao over 8 years ago in reply to carlos.ramos14

TI__Mastermind 49445 points

Carlos,

Yes, you have to be careful because there is no protection for hot swapping.

BR,
Koteshwar Rao

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ISO154X two battery I2C isolation