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Enable Mode in UCC28019

Koundinya Nellutla
Prodigy 20 points
Other Parts Discussed in Thread: UCC28019

To whomsoever it may concern, Hello I would like to use IC UCC28019 for Boost PFC Application. I want this IC to operate only when my microcontroller gives it a command. Can you suggest some method to achieve this?

  • 0
    TI__Mastermind 34465 points

    You can do this very easily by pulling the VSENSE pin below the enable threshold of 0.8V.

    Normally this is done by placing a transistor across the lower resistor in the VSENSE resistor divider chain.

    The UCC28019 is enable when the transistor is off.

    Regards,

    John Griffin

  • 0 in reply to John Griffin1
    Prodigy 20 points
    Thanks for the suggestion Mr.Griffin. We have implemented the same for a prototype but we feel that the closed loop control of the IC would be disturbed. We have seen multiple failures. Instead of the above, can the Vcc supply to the IC be swtiched on and off by placing a suitable MOSFET before the supply? Or any other solution without disturbing the closed loop?
  • 0 in reply to Koundinya Nellutla
    TI__Mastermind 34465 points
    Anytime you shutdown or startup the controller (whatever method you choose to implement) will disturb the closed loop nature of the control. The VSENSE enable threshold is the method that is normally used for a controlled startup or shutdown of the power supply. You can control the VCC also but you cannot place a MOSFET between the supply and the VCC pin. You need a low impedance ceramic capacitor on VCC in order to supply the high frequency switching currents to the UCC28019.
    If you are having component failures I recommend you investigate your circuit and pcb layout.
    You should try to capture some scope waveforms and investigate the failure mechanism.
    Regards,
    John