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UCC27531: Questions about the use of the UCC27531 PIN.

Grady Lee
Expert 2915 points
Part Number: UCC27531

Hi, TI expert.

My customer has a question about using the UCC27531 PIN.

Customer applies UCC27531, but it will be used as single, and negative bias will not be used.

Q1) Do you connect EN pin directly to VDD? Should I connect using a pull-up resistor?

If possible, I would like to use a pull-up resistor to connect, but how much should I use the resistance value?

(According to the company's regulations, floating pins are not allowed, and pull up or pull down resistors must be used.)

Q2) I am not going to use Negative Bias, how should I handle the OUTL pin? Should I connect directly to the OUTH pin?

Please Check. Thank you.

  • +1
    TI__Guru**** 189399 points

    Hi, Grady,

    As shown in the picture you posted, there is a 500 kohm resistor pulled to 5.8V internal VREF supply. Any external resistor will be in parallel with this.

    OUTH and OUTL don't have anything to do with negative voltage. They are used to independently tune the turn-on and turn-off times of the power switch being driven. Both Figures 41 and 45 show OUTL connected after the gate resistor on OUTH. this will allow the turn-on speed to be controlled by the series gate resistor, and the turn-off speed will be maximized. Previously, customers had to use a diode in series with the gate drive to accomplish this, and that resulted in a voltage drop, which slowed down the turn-off. So, this is a better technical for accomplishing tuning of turn-on and turn-off times.

    Let us know if you have further questions.

    Best regards,

    Don