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UCC27714: Schematic review

chentsu chung
Mastermind 6180 points
Part Number: UCC27714

Hi, 

Could you please help to check the schematic below? Thank you.

1. The COM should be connected to the VSS directly or connect to the GND of Low side MOSFET?

2. Please help to that is their needs to be modified.

Thank you,

C.T.

  • 0
    TI__Mastermind 23005 points
    Hello Chentsu,

    The UCC27714has the COM pin which is the driver current path return, and the VSS pin which is the control input ground reference.
    The COM pin should be connected to the low side FET ground reference to keep the gate drive current loop traces short.
    If there is a large ground place referencing the MOSFET source and control ground, is some cases it is OK to connect the VSS and COM together at the IC.

    Regards,
    Richard Herring
  • 0 in reply to Richard Herring
    Mastermind 6180 points
    Hi Richard,

    Thanks for your help, so how about the question 2? Is everything okey?

    Thank you,
    C.T.
  • 0 in reply to chentsu chung
    TI__Mastermind 23005 points
    Hello Chentsu,
    For the general schematic check, most components look like good initial value selections. I do have a couple of comments.
    On the boot diode MUR5320T3, I could not find a datasheet on the web. The boot diode needs to have a peak current rating to charge the boot capacitor thru the boot series resistance. The 3.3 Ohms will limit the peak current to <5A. We recommend a fast recovery diode so the boot capacitor is not discharged when the HS node switches high, 25ns to 35ns is a good trr target. A good general recommendation is the MUR160 or similar diode.
    The boot capacitor value of 1uF seems high compared to some applications. Review the guidance in the UCC27714 datasheet section 9.2.2 for the bootstrap capacitor value based on MOSFETs used and switching frequency.
    The other components are good values for this driver.

    Please confirm if this answers your questions.
    Regards
    Richard Herring