• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 2 answers
  • Subscribers 50 subscribers
  • Views 185 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

OPA551: Flap Output

Douglas Eaton
Prodigy 10 points
Part Number: OPA551

I am using the OPA551PA in a 8 channel application.
I was wondering what the Flag output looks like internally.
Can the Flags of multiple devices be Wired ORed together?
This will give me a system wide flag when any of the 8 devices shut down.
If they cannot be bussed together can I use simple diode ORing.
If not what would be the best solution.

  • +1
    Guru 140200 points

    Hi Douglas,

    I would do it with digital transistors (here only shown for four OPA551):

    What is a "digital transistor"?

    A digital transistor (here the MMUN2212) contains the actual transistor element and two bias resistors (here 22k) in one single package (here SOT-23).

    This approach has the advantage that the supply voltages of the individual OPA551 can drastically differ from each other. And it provides a perfect level shifting from the individual flag output potentials to the digital "high" and "low" levels without any risk of overdrive.

    Kai

  • 0
    TI__Mastermind 48086 points

    Hi Douglas,

    I think that Kai has answered your questions. Alternatively, you need to define a logic high and low for OPA551's Flag pin, convert the pin voltage to logic "1" or "0", and connect all OPA551's Flag digital logics and determine the system's Flag status through a logic IC or MCU, which is very similar to Kai's discrete method. 

    Best,

    Raymond

  • 0 in reply to kai klaas69
    Prodigy 10 points

    Thanks! That's an excellent solution.

    I'm doing development work with thru-hole devices.

    I found TO-92 digital transistor FJN3303R available from Mouser.

    It is obsolete, but I'm not planning on using it in production.

  • 0 in reply to Douglas Eaton
    Guru 140200 points

    Hi Douglas,

    you can easily replace the digital transistors by discretes. They have only been suggested to save PCB area. A BC550B could be used or almost any other small signal NPN transistor Relaxed

    Kai

  • 0 in reply to kai klaas69
    Prodigy 10 points

    Thanks for the reply! I am doing a Proof of concept prototype with thru-hole parts. I do want to limit parts count by using digital transistors. In production I plan to test surface mount parts.

  • 0 in reply to Douglas Eaton
    TI__Mastermind 48086 points

    Hi  Douglas,

    I am going to close this inquiry. If you have additional questions, you are still able to open this thread or create a new one via E2E forum. 

    Best,

    Raymond