• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 64 subscribers
  • Views 195 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.

UCC28782EVM-030: EVM shutdown in <65W load

Toshiro Imi
Expert 7260 points
Part Number: UCC28782EVM-030
Other Parts Discussed in Thread: UCC28782

Hello,

Our customer has evaluating 65W audio by using UCC28782EVM-030 however UCC28782AD seems to be sutdown less tthan 65W load.  He did not idenitfy the reason but he suspected UCC28782AD was shudown by OPP or OCP so asked us how he can resolve it. Could you plase advice us which expernal parametr show be modified ssuming this issue was happened by OPP or OCP.

when I checked the schematcis as well as UCC28782 datasheet, it says ROPP resistor connected between CS and current sense resistor is able to optimize OPP threshold. Would you please help us the customer can resolve his issue by adjusting following R19. 

  • 0
    TI__Mastermind 24375 points

    Hi Toshiro-San,

    Thank you for the query on UCC28782.

    OPP/ OCP can be confirmed from the following table by observing the sequence of events leading to this. Please probe the Vcst pin.

    OPP is a e feed-forward signal to vary VCST(OPP) depending on VBULK voltage. As ROPP (R19) increases, the OPP trigger point becomes lower at high line, so lower peak currents circulate to maintain  OPP trigger point constant over a wide line voltage range. This generally needs to be adjusted if you observed variations as you vary the line voltage from a lower to higher input voltage.

    OCP can be triggered due to improper choice of R47 or could be due to spikes observed on the CS signal. This might require tuning the capacitor C21 on CS pin (placing it close to the pin) and djusting (reducing) the value of R47 also.

    Please let us know if you have any questions.

    Regrads,

    Harish

  • 0 in reply to Harish Ramakrishnan5
    TI__Expert 7260 points

    Thank you very much !!

    I will introduce your suggestin to our customer and cechk if he can resolve his issue.

    Best regards,