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UCC28720: Vs pin left floating

Adam Daluga
Expert 6545 points

Part Number: UCC28720

Hello,

We are looking at using UCC28720 in a buck regulator.

Does the Vs pin (pin 2) have to be connected to the output voltage in order to function properly?

 What would happen if we left the Vs pin unconnected?

Would the part still function?

Just curious how this pin comes into play for the parts’ operation.

 

Thanks,

Adam 

  • 0
    TI__Guru* 86286 points

    Hello,

    I have received your inquiry and it is under review.  I will get back with you shortly.

    Regards,

  • +1 in reply to Mike O'
    TI__Guru* 86286 points

    Hello,

    I have found reference design using the UCC28720 in a high side buck in the following link .  You can, use this as a reference on how to use this device in  a high side buck.

    https://www.ti.com/tool/PMP9649

    The UCC28720 was designed for primary side regulation control and uses the VS to sense the transformer turs ratio to sense the output voltage to adjust the peak current and switching frequency to control the duty cycle.  In a buck application the VS pin is used to sense the output voltage with a resistor divider.  Please refer to the PMP6949 reference design in the link above.  For this to regulate the output voltage in a buck or flyback requires using the VS pin.  

    If this resolved your inquiry please select resolved at the end of thread.

    Regards,

  • 0 in reply to Mike O'
    TI__Guru* 86286 points

    Hello Adam,

    I am just checking in.  If this resolved your issue could you select resolved at the end of the thread?

    Regards and Thanks,

    Mike