• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 19 subscribers
  • Views 272 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

TXU0104: VOH Specification & Behaviour when Outputs Connected to Damaged Ports

TXU0104: Datasheet Paragraph 9.3.5 Clarification

Bogdan Banik
Prodigy 30 points
Part Number: TXU0104

TXU0104 datasheet paragraph 9.3.5 specifies that "... It is
recommended that the inputs are kept low before floating (disconnecting) either supply..."

What does this mean?

I interpret the rest of paragraph 9.3.5 to mean that is either the VCCA or VCCB power rails is interrupted (ie. goes down), then the TXU0104 puts its A-Side inputs and B-Side outputs into a high-Z state thereby essentially disconnecting itself from the rest of the surrounding electronic circuit. This is perfect for my application.

I am however not sure what to make of the statement identified above. If by "floating (disconnecting) either supply" you mean power goes off in either supply, then I question whether or not I have a problem... I am not monitoring VCCA or VCCB power rails so cannot anticipate if and when power in either goes down; hence do not have time to put the TXU0104 inputs in a logic-low state.

Please advise how the TXU0104 behaves with random (ie. unpredictable) VCCA or VCCB power rail failures.

Cheers, B Banik

  • 0
    TI__Genius 16735 points

    Hi Banik,

    The TXU0104 has CMOS inputs which do not like a floating input when its supplies are ramped. So the reason the paragraph says to keep inputs low prior to floating the supply is because if input A is high and you float your input supply A from a high state (ie 5V), then your supply A will take a long time to discharge to a 0V during which time, you could see high supply currents in supply B or even incorrect outputs on output B.

    If your supply A is ramped down to 0V and then floated, then you have nothing to worry about. When supply A reaches 0V, your inputs will go Hi-Z like you mentioned and you should see no problems.

    Regards,

    Karan

  • +1 in reply to Karan Kotadia
    Prodigy 30 points

    Thanks very much Karan... this does indeed resolve my issue... your help is very much appreciated!!