Other Parts Discussed in Thread: ISO7721
What is the frequency of the internal oscillator used for low frequency signals? I am putting 24 of these in a piece of equipment and don't want issues passing FCC EMI tests. Thanks,
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Hi Jonathan,
Thank you for providing more details regarding your application and emissions requirements. Please note that the absolute power levels of switching in power supply and data switching in digital isolators will be many folds different. Hence emissions from digital isolators are generally much lower than what you see from power supply switching. The internal oscillator, especially, would be further lower in power levels and local to their respective die (Die1 for VCC1, Die2 for VCC2).
Unfortunately I do not have emissions test data for ISO7421 to share with you. I do have CISPR 22 Class B emissions test result of ISO77xx, please find the results pasted below. From the test results, you can see that there is no contribution from ISO77xx for emissions and you only see the noise floor. As mentioned earlier, this is due to the low power levels of data being processed inside device. Even if you use 48 devices of ISO7721, it shouldn't be a problem.
ISO77xx-Q1 is also being successfully used in automotive applications whose emissions requirements are much more stringent than industrial emissions requirements.
I hope that answers your questions, thank you.
Regards,
Koteshwar Rao