• State TI Thinks Resolved
  • +1 person also asked this people also asked this
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 64 subscribers
  • Views 147 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

UCC28742: Brown-out feature and differences between UCC28740 vs UCC28742?

AnBer
Mastermind 28970 points
Part Number: UCC28742
Other Parts Discussed in Thread: UCC28740, , PMP

Team,

-Brown-out:
With both UCC28740 and UCC28742 controllers, a brown-out function can be set via the resistors on the VS pin.
Do we have more information on the Brown-out function?
In the data sheet of the UCC28740 the brown-out function is mentioned at page 19, but unfortunately no further description:
https://www.ti.com/document-viewer/UCC28740/datasheet/design-requirements-slusbf42831#SLUSBF42831
Is this function integrated via the HV pin?

Do we have PMP/TIDA ref design that make uses of brown-out features?

-UCC28740 Vs UCC28742:
[EDITED]
I found the below post that provide more information on the UCC28740 vs UCC28742 differences.
Are there some other differences to consider?
https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/707968/ucc28742-choose-between-ucc28742-and-ucc28740-and-take-advantage
https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/992798/ucc28740-the-major-difference-between-ucc28740-and-ucc28742

Thanks in advance,

A.

  • 0
    TI__Expert 5486 points

    Hi Anber, thanks for your question

    For UCC28740, the brown out voltage specified in the datasheet is the voltage when the device will turn on. Rs1 (voltage divider top resistor at VS pin) is designed to set the minimum voltage from the AC line to pull up Ivsl_run current from the IC through VS pin. For UCC28740 this current is 225uA typical value and the EVM and datasheet have a Rs1=105Kohms to turn on the device at ~68Vrms. 

    Brown out voltage is a fault voltage from the input line at which the controller will still switching. The datasheet typical application is using brown out voltage a little bit different than that.

    UCC28740 vs. UCC28742: Those two E2E explained very well. But here a summarize of the main differences:

    1) HV start-up for UCC28740. It provides a faster turn on response, lower stand-by power, but requires more footprint space for the JFET. That is why UCC28742 is smaller and cheaper, but it has higher stand-by power and lower turn on response.

    2) Constant current-CC mode for UCC28740. When maximum output current Ioutmax is set at the output, the device moves to CC mode, then the device will still be switching at Ioutmax but the output voltage Voutmax losses regulation. UCC28742 instead, will shut down and try to restart if Iout decreases to Iout<Ioutmax in less than 120ms. 

    If you have any further questions, please let me know replying to this thread.