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UCC27531: Resistor on the OUTH pin

HPB
Expert 1350 points
Part Number: UCC27531


Hi! The datasheet for this part shows a resistor on the OUTH pin. However the EVM schematics show a 0R resistor. How is the value of this resistor calculated? Also is it necessary to connect this resistor or simply tie the OUTH and OUTL together? I'm planning to drive a single MOSFET with this device. 

  • 0
    TI__Genius 13445 points

    Hello HPB, 

    Thanks for reaching out, my name is Mamadou Diallo from the High Power Drivers' team.

    The gate resistance values on OUTH and OUTL are dependent on your desired turn-on/off times of the power FETs your driving. High values resistor on OUTH will lead to lower gate (source) current therefore extending turn-on times while higher values on OUTL will impact turn-off times therefore. This will impact the switching losses of the FETs.

    You typically want minimal gate resistance on OUTL(0 to 2-Ohms) while adjusting resistance on OUTH (>2-Ohms) based on peak current requirement out of gate driver, turn-on time of the MOSFET and gate charge.

    I suggest a 0-Ohm gate resistance (placeholder) on OUTL and depending on the MOSFET used, 2 to 10-Ohms on resistor on OUTH.

    I have attached few documents discussing these topics in details.

    http://www.tij.co.jp/jp/lit/an/slla385/slla385.pdf How to size external gate resistance

    Section 3.1 of the document: http://www.ti.com/lit/ml/slua618a/slua618a.pdf

    Peak source/sink current estimations 

    Please let us know if you have further questions or press the green button if this addressed your questions.

    Regards,

    -Mamadou