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UCC27282-Q1: Does it have recommended continuous current and recommended peak current on its bootstrap diode?

Yoshiki Ochi
Expert 7975 points
Part Number: UCC27282-Q1

Hi team, 

Does UCC27282-Q1 have "recommended continuous current and recommended peak current" on its bootstrap diode?
Does it has internal current limitation resistor in series to internal bootstrap diode?
How do we select external current limitation bootstrap resistor value if it is needed? 

Regards,
Ochi

  • +1
    TI__Genius 9301 points

    Hi Ochi, 

    The diode average current should be kept below 80mA. They can calculate the current using the switching frequency (Fsw) and the total charge (Qg) of the FET connected to HO pin (I = Qg*Fsw).

    There isn't a resistor in series with the internal bootstrap diode inside the device (please refer to datasheet section 7.2 "Functional block diagram). The dynamic impedance of the diode (typically 1.5 ohm) naturally limits the peak forward current and prevents any damage for most applications. In some applications where switching frequencies are very high (e.g. higher than 1MHz) and the low-side minimum pulse width is very small, the diode current could be very high and in these cases we would advice to use an external schottky diode. It it good to have a placeholder in the board for an external diode if possible.

    To select the bootstrap circuit components, including the bootstrap series resistor, please refer to this application note: https://www.ti.com/lit/an/slua887/slua887.pdf

    Best regards,

    Leslie

  • 0 in reply to Leslie Marquez
    TI__Expert 7975 points

    Hi Leslie, 

    Thank you. How about abs max current? Its start up condition looks worst case or no bootstrap capacitor charge, which leads high peak current for startup through bootstrap diode. So I would like to abs max peak current capability to make sure we do not need bootstrap capacitor. 

    Regards,
    Ochi

  • 0 in reply to Yoshiki Ochi
    TI__Genius 9301 points

    Hi Ochi, 

    I sent you an email earlier today regarding the peak current. 

    You mentioned you want to make sure you do not need a bootstrap capacitor. Can you please clarify what you mean by this? The bootstrap capacitor provides the bias/supply for the high side driver, so it is needed. 

    Best regards,

    Leslie

  • 0 in reply to Leslie Marquez
    TI__Expert 7975 points

    Hi Leslie, 

    Sorry for typo. I would like to know bootstrap current limit resistor requirement instead of bootstrap capacitor. I will ask another question via email you sent to me.  

    Regards,
    Ochi