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UCC27712: How to determine peak current of UCC27712 driving mosfets?

Karlis Tucs
Expert 1385 points
Part Number: UCC27712

Hi. I want to drive 2 mosfets BUK9Y11-80E and PSMN025-80YL with UCC27712. 

I did all calculations described in the datasheet, but one thing is not clear for me, how to calculate the peak current.

I found calculation like this:

dT = [dV x C]/I 

where dT= turn-on/turn-off time, dV = gate voltage, C = gate capacitance, and I = MOSFET peak drive current.

Should I take the 1.8A from UCC27712 datasheet and calculate the turn on time or should I take rise time of mosfet from mosfet datasheet and calculate the peak current?

What would be the correct aproach to this? I do not want to burn down the UCC27712.

Thanks in advance!

  • 0
    TI__Mastermind 33660 points
    Hi Karlis,

    I am an applications engineer supporting UCC27712. Thanks for your interest!

    The datasheet value of 1.8A should be considered the typical peak output current during rising or falling edges, and the output current is limited internally to approximately this value. The current will change as the gate voltage of the MOSFET increases (rising edge) or decreases (falling edge). Depending on the size of the gate resistor used, the peak current may also be less than 1.8A (e.g. 12V drive voltage, 10Ω combined gate drive resistance, peak current will be 12V/10Ω = 1.2A).

    Calculation of turn-on and turn-off time can be approximated by the method you described, but be aware that this approximation will underestimate the real turn-on and turn-off times, since it assumes the UCC27712 behaves like a current source. Rise and fall time are heavily dependent on MOSFET parameters, external gate drive resistance, and system values such as drain current and switching voltage.

    If the primary concern is avoiding damage to the UCC27712, TI recommends using the power dissipation calculations included in the datasheet.

    Regards,
  • 0 in reply to Derek Payne
    Expert 1385 points
    Hi Derek. Thank you for answer.
    Ok , I did the calculations and the power dissipation is ok in my application