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UCC28600 Start-up time

tateo yamashiro
Guru 10890 points
Other Parts Discussed in Thread: UCC28600, UCC28740

Hi

My customer has question about UCC28600.
Could you tell me about question.

[Question]
My customer wants start-up time is faster. So my customer change Rsu=1Mohm to 500kohm and start-up time is faster.
But when converter is no load, IDD is bigger than Istanby(350uA typ).
And VDD is clamping by internal diode and VDD become to 26V. My customer has questions.

- When I want start-up time is faster, is this method the best? Do you have a any idea? *I can't change Cdd.
- If this method is OK, what is max VDD current?

Please show attached file.

2364.Question of UCC28600 start- up time_20141119.xls

Best regards,

tateo

  • 0
    TI__Mastermind 34465 points

    Tateo san,

    I suggest that you consider using the UCC28740 in place of the UCC28600.

    The UCC28740 has an internal high voltage start that is disabled when the power supply is operational. Also it has lower standby and operating current levels.

    The issue with the UCC28600 is that it continues to draw a small current from the HV line during operation.

    The max VDD current is specified in the data sheet as 7mA at 130kHz for the UCC28600.

     

    Regards,

    John

  • 0 in reply to John Griffin1
    Guru 10890 points

    Thank you for your reply.
    My customer want to use UCC28600. Because design is almost finish and UCC28740 is low gate drive current.
    My customer have more question.

    When output is noload and internal diode is break down and VDD become 26V, my customer is worried about internal diode will be destroyed.
    So my customer want to know how much current can diode pass?
    And my customer want to know power dissipation of internal diode.

    Best regards,

    tateo

  • 0 in reply to tateo yamashiro
    TI__Mastermind 34465 points

    VDD is rated to a clamped current of 10mA and  a power input of 320mW