• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 38 subscribers
  • Views 429 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

PMP4745: Drive Current

Julian Chen
Expert 2550 points
Part Number: PMP4745
Other Parts Discussed in Thread: TPS23757

Hi E2E,

Our customer refer PMP4745  to design TPS23757.

But the MOS which customer use that had higher Qg lead to VGS can't pull low at the moment. (Please refer the waveform)
(Customer MOS's Qg=42nC, PMP4745 MOS's Qg=17nC)

We modify R12 to 43.2R  can fix this issue. (the Q1 Gate can pull low fast)

Could you let us know does have any risk with modify R12 to 43.2R?

Thanks!

Circuit:

Waveform: 

  • 0
    TI__Mastermind 41800 points
    Hi Julian,

    If you reduce base resistor down to 43.2 ohms then the BJT will need be higher rated. Probably the lowest you should go is half the 5k resistor with that BJT. The tradeoff is efficiency. I've seen designs that add a resistor across the gate to ground as well to speed up the shutoff.