• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 125 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.

TPS54360: Keep device on the board without VIN

Brian Wang0
Expert 5310 points
Part Number: TPS54360

Hi team,

Here is a request from my customer trying to confirm their design.

In one of their design, they have a TPS54360 on board with full circuit. A special case is under some conditions, they won't apply any voltage on VIN, but a voltage might be applied to Vout Pin. Customer would like to know whether there is any risk of doing this? Since no MOS switching would happen when VIN=0, it seems the buck circuit should be already, but they want to confirm whether there is any internal circuit which may not accept the vout when Vin =0?

Regards,

Brian

  • 0
    TI__Guru 72375 points

    Hello

    Usually it is not a good idea to allow voltage on the output of a regulator when the input is zero volts (or even floating in some cases); this

    include the TPS54360.

    This is because there is a diode between the drain(VIN) and source(SW) of the power MOSFET inside the converter.

    With a voltage on Vout, and the input held at zero volts, there will be a path from Vout to Vin through the inductor and this diode.

    Even if the input is floating, a current will flow and try to charge the input caps, possibly to a high voltage due to resonance

    with the caps and the inductor.  This phenomena has been seen in the past under some conditions.

    Allowing current to flow through this diode can cause a parasitic to turn on or even damage the diode.  Since it is not a "true" diode

    but a parasitic formed when the MOSFET is constructed on the die, it is not designed to take current for more than a few 10s-100s nsec.

    We recommend that you use a diode between input and output to provide a path for any reverse current. Or a blocking diode could be

    used on the output.  You can increase your programmed output voltage slightly to counteract the drop of the blocking diode,

    if required.  The diode should be a Schottky.

    Thanks

  • 0 in reply to Frank De Stasi
    TI__Guru 72375 points

    Hello 

    I hope your question has been answered.

    I will close this post due to inactivity.

    Thanks