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THVD1452: Pin 13 (VCC) - Can it be left floating?

Roy Hsu
Genius 9350 points
Part Number: THVD1452


Hi Team,

We were thinking about replacing the SP491E with the THVD1452 and we found that pin 13 is NC for the SP491E, while it's Vcc for the THVD1452.

Since the datasheet mentions that pin 13 and 14 are internally connected, can we leave pin 13 floating so that we can drop-in the part directly?

Thanks!

Roy

  • 0
    TI__Guru 52702 points

    Hi Roy,

    So the short answer is yes, but there are going to be some changes to part performance. 

    Since they are internally connected - connecting one to VCC is essentially connecting both to VCC. However the big difference between this package and the package with 1 VCC pin is the thermal to ambient thermal resistance is higher - when you don't have both VCC pins connected the device will heat up quicker as all the supply current will see a larger resistance as there is only one entry point. I doubt it will heat up as quick as the other package but it will not perform at its best when this is done. If possible - since the pins are right next to each - adding a trace to short them together would be the preferred solution - however if the extra thermal impedance is okay for the application it can be done.

    Please let me know if you have any other questions!

    Best,

    Parker Dodson

  • 0 in reply to Parker Dodson
    TI__Genius 9350 points

    Hi Parker,

    Thank you, that's very informative! So the THVD1452 does not seem to be the best fit for this if the existing PCB can't be changed. I searched for a few other parts but all of them also have Pin 13 as Vcc. Do you have any recommendation to replacing the SP491E without having to change the PCB layout?

    Thanks!
    Roy 

  • 0 in reply to Roy Hsu
    TI__Guru 52702 points

    Hi Roy,

    I'd say it probably is the best fit if you want pin to pin. As mentioned above - they are internally connected so if one of them is floating it will still be powered (we put that note in the datasheet for that reason as we were aware of similar packages having an N.C. in their design) as long as the other pin is connected to VCC. It will should still perform decently well - its just the junction may heat up a bit more quickly than if both are connected - however this affect shouldn't be large enough to degrade the temp. spec (as there are smaller packages that would still have higher temperature coefficients). In all honesty it would probably perform similarly (in terms of heat) to comp here as the comp only has 1 power pin - so you just aren't getting that benefit - but I think from an operational point of view its fine.

    Please let me know if you have any other questions!

    Best,

    Parker Dodson