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LM5050-Q1 OR function

Natallia Holubeva1
Expert 6550 points

Hello team,

Can we control on/off with just the OFF pin? The functional block diagram has an OR gate between IN/OUT/OFF. Sect 7.3.3 contradicts the function block diagram.
How often can they turn the chip on and off? How many times can we turn the device on/off before they effect the FIT rate of this device?

 

 

 

Thank you!

  • 0
    TI__Genius 12621 points
    Hi Natallia,

    To understand the purpose of the LM5050's OFF pin, check out this E2E thread:

    e2e.ti.com/.../526431

    Thanks,
    Alex
  • 0 in reply to Alex Triano
    TI__Expert 6550 points
    Hi Alex,

    I am not sure I understand your point. My first question is:

    - It looks like the differential voltage between IN and OUT pins can turn the IC ON. This is something I need to avoid.
    In the functional block diagram, both the comparator of the differential voltage and the shutdown input go to the OR ring. Then, the section 7.3.3 contradicts the block diagram.

    Second question is about the FIT data. I don't think it is covered at all in the link you have referred me to.

    Thanks!
    ~Natallia
  • 0 in reply to Natallia Holubeva1
    TI__Genius 12621 points
    Hi Natallia,

    I just spoke to Steven to clarify some questions. But overall, the OFF pin is not an Enable/disable. It is used to turn off the MOSFET to check if the FET is damaged (but current will still flow from IN to OUT through the body diode of the external FET), or can be used to prevent oscillations in redundant systems.

    The IC is always ON and current is always flowing from IN to OUT if there is a voltage at VIN. That is the intention of an ordinary ORing controller - to simulate a diode with low loss.

    If ON/OFF functionality is needed, something like this may be of use:
    www.ti.com/.../TIDA-00233

    Regarding FIT data, I'm not sure how to answer the question. The OFF pin should not be used to repeatedly turn ON/OFF the MOSFET. TI has an estimator tool which can be used to find the FIT data for this IC:
    www.ti.com/.../estimator.tsp

    Thanks!
    Alex