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LM5119

eli
Guru 13485 points
Other Parts Discussed in Thread: LM5119, UCC27211, LM5116

Got the below question:

I'm using TI UCC27211 driver to drive the buck MOSFETs and I want to make sure I'm connecting the LM5119 correctly. In order to drive the high side input of the UCC27211, I connected the LM5119 SW pin to GND and the VCC pin directly to HB pin (without a diode).

  • 0
    TI__Guru 58351 points

    Hi

    Electrically, your connection is right , but by connceting SW node to GND, LM5116's dead-time might be affected, the dead-time have to be guaranteed by UCC27211 operation. Diode emulation will not work well, FPWM is recommended.

    Regards,

     

  • 0 in reply to EricLee
    Guru 13485 points

    I got the below aditional question:

    I have another technical issue regarding the LM5119:

    In my design I have an auxiliary 8.8V which is always valid (even before the LM5119 turns on).

    I'm using this Auxiliary voltage to power the LM5119 VCC pin through a schottky diode.

    My question is whether I can eliminate the additional schottky diode between VCC and HB pin; that is connect the 8.8V through a diode to the VCC and the HB pins together and disable the internal VCC regulator by permanently pulling it above 1.25V.

  • 0 in reply to eli
    Guru 13485 points

    Hi,

    1.Any feedback?

    2.Also,would like to add to the below question:

    I'm using the LM5119 in a dual interleaved mode buck converter design.

    The question is whether it's possible to connect the VCC1 and VCC2 pins together (shortcut the pins) and power them through a schottky diode from the auxiliary 8.8V (as described in the previous question) while permanently disabling the internal regulators.

    May I emphasize again that the auxiliary voltage is always on.

  • 0 in reply to eli
    TI__Guru 58351 points

    Hi

    You can remove the diode connecting from VCC to HB if VCC is tied to HB ans SW is connected to GND.

    Connecting VCC1 and VCC2 together is not recommended. You may need two diodes one from AUX to VCC1&HB1, the other from AUX to VCC2&HB2

    Regards,