• State
  • Locked Locked
  • Replies 2 replies
  • Subscribers 63 subscribers
  • Views 458 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.

UCC28070 PFC Vsense current

Robert Caruana
Prodigy 100 points
Other Parts Discussed in Thread: UCC28070

Hi guys, I'm looking to use the UCC28070. Datasheet says that typ. Vsense input current is 250nA. Now when I calculated the current through the resistor network in the SLUA479B App Report, the current is to the Vsense input is 129uA. Is this ok and why? If so what's the typ. current allowed to this pin? Thanks

  • 0
    TI__Mastermind 34465 points
    Hi Robert,
    The output voltage of the EVM is 390V and this is divided down by 3 series connected 1 MOhm and a 23.2 kOhm resistor. This will result in a 129uA sense current as you point out.
    Typically the input bias current to the sense amplifier is 250nA.
    This would result in a sense error of 0.25/129 or 0.2%
    You could decrease this error by increasing the current in the sense leg but this would increase the power losses in the system
    Hope this helps
    Regards,
    John
  • 0 in reply to John Griffin1
    Prodigy 100 points

    Hi John. thanks for your reply. I didn't know that. I guess it's something that comes with experience. I asked at work about my issue and I got it all wrong, the way the current works I mean. It's all fine now. But thanks for that. I'll take it into consideration.

    Its a bit difficult for me to understand the circuitry around the current sensing in this report. Can some one kindly explain how it actually works or point me to where I can understand it?  Thanks