ISO7021: Can the ISO7021 perform logic translation between a 1.8V supply and a 3.3V or 5V supply?

Andrew Loblaw

Part Number: ISO7021

The datasheet recommend operating conditions suggest that if one side is at 1.8V supply, then the other side can only be between 1.71 -> 1.89V.

Does this mean that it will not work with a 1.8V supply and a 3.3V supply, or am I misunderstanding this table?

over 3 years ago

+1 Koteshwar Rao over 3 years ago

TI__Guru 53855 points

Hi Andrew,

Thanks for reaching out and for your interest in ISO7021.

The datasheet does provide electrical and switching characteristics specifications for the conditions where VCC1 and VCC2 are the same. This was done simply to minimize the permutations/combinations created from VCC1 and VCC2 otherwise, these two are independent supplies powering independently ground referenced circuits. Hence, the supply voltage of VCC1 and VCC2 can any voltage in the recommended operating voltage range irrespective of the other supply voltage. This means that applying 1.8V for one supply and 3.3V or 5V for the other supply is absolutely not a problem.

Please see below FAQ on the same topic, this applies to ISO7021 as well. Thanks.

https://e2e.ti.com/support/isolation-group/isolation/f/isolation-forum/732656/faq-can-i-power-the-two-sides-of-a-digital-isolator-with-different-voltages

Regards,
Koteshwar Rao

Isolation

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ISO7021: Can the ISO7021 perform logic translation between a 1.8V supply and a 3.3V or 5V supply?