• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 63 subscribers
  • Views 598 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.

UCC28700: Start Up Issue

Mihir Gupta65
Intellectual 2155 points
Part Number: UCC28700

Team,

I have a customer who is evaluating the UCC28700 and is having some trouble starting up his circuit. They have modified the UCC28700 EVM with the values as shown in the attached schematic.

20180126_Schaltplan.pdf

However, even with a VDD of 21V, they are only seeing 3 pulses at the DRV pin of the UCC28700. The waveforms are shown below:

CH1 :        U1-DRV
CH2 :        U1-CS
CH3 :        U1-VS
CH4 :        U1-VDD

It looks like the UCC28700 is going into a fault mode. Do you have any insight as to why this might be happening?

Thanks and Regards,

Mihir Gupta

FAE - South Germany

  • 0
    TI__Expert 7080 points
    Hi Mihir,

    Thanks for your interesting in TI's product.

    I think this fault mode was input Brown_IN , based on the parameters you provided , I calculated the brown_in voltage is 89.1Vdc.
    But your input voltage range is 37~41V. you can find the calculation equation on datasheet page 10th.

    So I suggest you decrease the value of R4 & R9 to meet your input range and output regulation.

    Thanks.