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UCC24610 Ton pin and lowest recommended Rds(on) for SR FET question.

pulseENG
Prodigy 30 points
Other Parts Discussed in Thread: UCC24610

Hello Ti Support Forum,

I have two questions related to the UCC24610 SR Controller.

1. Ton pin 3 is stated to have an internally regulated 2V supply. By setting an external resistor from this pin to ground, a current is set which sets the Ton blanking period. Is this 2V signal from the Ton pin, supposed to be stable throughout normal Run Mode operation, or does it droop to the point where a threshold is reached and the device Run Mode is disabled?

2. My second question relates to the MOSFET(s) this controller is driving. What would be the lowest recommended Rds(on) and Gate charge total on the FET that is being driven by the UCC24610?

Thanks for any help that can be offered.

 Jason.

  • 0
    TI__Genius 15910 points

    The 2V regulator is supposed to be stable throughout the entire operating range.  Check to make sure your layout has the shortest traces possible for TON and that the traces are not located so that they would pick up noise from the switching node.  Noise pick up on TON could destabilize the internal 2V regulator.  Another way of destabilizing the internal regulator is by adding capacitance to the TON pin; the layout should be good enough that an external capacitor is not needed for noise filtering, a capacitor greater tha 100pF max is not recommended.

    The Rdson of the SR FET should not be too low, yes, higher Rdson is better for the UCC24610.  A lower Rdson would result in the -5mV threshold being crossed with more currrent, and that "more current" will have to go through the body diode.

    Refer to the attachment for SR FET selection tips.

     

     

    UCC24610 SR FET selection.pptx