ISOW7821: Question about high isolation voltage condition

Hi Satoshi-san,

Thanks for using our E2E forums.

1). Technically, yes - one can cascade isolators to achieve higher isolation voltage ratings. However, before we consider that option, there might be better solutions available based on end equipment needs. For example, one can use the ISO7821 (no W in the part name; only data isolator without power), which can support 2121V (DC) and 5700V rms (1 minute) in the same footprint (16DW). You can then use an SN6505 part to drive a transformer to get isolated power. The 10mA load current budget at 5V should be easily handled since the 6505 can provide up to 1A of current.

Can you please share more details on the end equipment that needs this high isolation voltage Vac spec? 

2) We will follow-up with you on this. The ISO7821  (no "W") part linked above contains the capacitor lifetime data in the datasheet, but this is for data path only. We will try to see if we can provide a similar curve for the W parts also [data + power].

3) This data unfortunately cannot be shared on a public forum. Sharing this will require an NDA and we will have to pursue this offline over PM/email.  Is this something you wish to pursue? If yes, can we please reach out to you/your end customer over email to route this through the correct channels?

Best regards,

Abhi

Hi Satoshi-san,

Abhi is going to be Out Of Office, so please allow me to help you while Abhi is away.

1) Abhi already addressed this question.

2) ISO7841 datasheet has the lifetime data published in Section 6.18 as Insulation Characteristics Curves, this will equally be applicable for ISO7821 as well. ISOW7821 lifetime curve will be slightly different from ISO7821 for the reason that ISOW7821 includes an integrated DC/DC converter as well. Like Abhi asked earlier, can I reach out to you through on your email that you have used for E2E profile creation for sharing you lifetime curve?

3) Regarding the failure mode, before I comment on this can you please describe more about what exact data are you looking for?
If it is about whether the isolation barrier is going to fail-open or fail-short, then please refer to the white paper at below link.
www.ti.com/lit/wp/slyy081a/slyy081a.pdf


Regards,
Koteshwar Rao

Satoshi-san,

I have sent you an email with the requested information. I will go ahead and mark this thread as closed. If you have other questions, please create a new E2E post. Thanks.


Regards,
Koteshwar Rao