TXS02612: SEL Pin Behaviour When VCCA Powered Down

Jonathan Garnier

Part Number: TXS02612

Tool/software:

Hi there, I have read that the SEL pin circuitry is powered by VCCA. What happens when VCCA and VCCB are both powered, but then power is removed to VCCA?

My use case is when the host on port A has its power cut, but the device on Port B is still powered. I want to check that there is isolation between the ports to prevent any back-powering. I only have port B0 connected, port B1 is left unconnected so I assumed I can just select the other port which would disconnect the lines, but am concerned that the SEL pin might not behave it VCCA is not powered at all. Any advice or feedback is appreciated.

1 month ago

0 Joshua Salinas 1 month ago

TI__Mastermind 26440 points

Hello Jonathan,

We are looking into this and will respond by today.

Regards,

Josh

0 Joshua Salinas 1 month ago

TI__Mastermind 26440 points

Hello Jonathan,

With VCCA off (or disconnected), SEL status will be undetermined since it no longer has a reference voltage.

Regards,

Josh

0 Jonathan Garnier 1 month ago in reply to Joshua Salinas

Prodigy 20 points

Hi Joshua, thanks for your reply!

So in that case, say I just tied the SEL pin LOW, will this still always select port B0 as GND is still referenced? Or is there other circuitry involved here that requires VCCA even to select port B0?

And a follow up question, is it a problem if VCCA is off or disconnected, and then gets turned back on? This is while VCCB is always active.

Thanks,

Jonathan

+1 Joshua Salinas 1 month ago in reply to Jonathan Garnier

TI__Mastermind 26440 points

Hello Jonathan,

With VCCA off, there isn't a good way to determine SEL state even if SEL pin is tied LOW.

The only problem I see is unwanted output glitches when turning on VCCA. See more information below

https://e2e.ti.com/support/logic-group/logic/f/logic-forum/1469104/txs02612-can-vcca-and-vccb0-b1-be-power-up-at-the-same-time?tisearch=e2e-sitesearch&keymatch=TXS02612.

Regards,

Josh

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TXS02612: SEL Pin Behaviour When VCCA Powered Down