TXS0108E: Behavior when OE = VCCA = 0V, while VCCB = 3.3V

Antenna_Head

Genius 12740 points

Part Number: TXS0108E

Team-

This is concerning a power up sequence and/or failure mode of a product using the TXS0108.

Suppose that OE = VCCA = 0V, while VCCB = 3.3V. (Obviously, this is not how the part is supposed to be operated)

What does the B port look like?

Are the pins pulled up the VCCB through Rpub has shown in the figures of the data sheet?

Thanks, Best, S. Dunbar, AFA Coloradao

over 8 years ago

0 aozer over 8 years ago

TI__Mastermind 30375 points

Hello,

If any of the supplies are at ground, all of the I/O ports will be in a high impedance state. The internal pull-ups will not be active.

0 Antenna_Head over 8 years ago in reply to aozer

TI__Genius 12740 points

Thanks for the response;

Your description is contrary to the simplified diagram in the data sheet, though I think the behavior of the pull-ups is described (as you did) on page 17.

0 aozer over 8 years ago in reply to Antenna_Head

TI__Mastermind 30375 points

That is because it is a simplified diagram, it doesn't show all of the actual internal circuitry. It is only provided to give a basic understanding of how the outputs are driven.

I just tested it in the lab to verify and I can ensure that if any one of the supplies are at ground, regardless of the state of the OE pin, all I/O ports will be in a high impedance state and the internal pull-ups will be disabled.

0 Antenna_Head over 8 years ago in reply to aozer

TI__Genius 12740 points

Thanks very much for verifying... maybe would be good to add a few sentences clarifying this somewhere in the data sheet- I know other level shifters generally clarify this. Thanks again!

0 Antenna_Head over 8 years ago in reply to aozer

TI__Genius 12740 points

Please contact me internally, we have some data that contradicts your results. thanks, Best, S. Dunbar, AFA Colorado

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TXS0108E: Behavior when OE = VCCA = 0V, while VCCB = 3.3V