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UCC28750: Regarding the cycle-by-cycle peak over-current limit

Kyohei
Expert 1440 points
Part Number: UCC28750
Other Parts Discussed in Thread: UCC28630

Tool/software:

Hi team,

Is it correct that the CS pin range of the UCC28750 can trigger over-current protection if it exceeds 200mV?

Also, if I select a product with a Latch type PROTECTION RESPONSE, the 7.4.4 Fault Protections section only mentions OSCP, but is it correct to understand that recovery from the Cycle-by-cycle peak over-current limit state is Auto retry?

Best regards,

Kyohei

  • 0
    TI__Genius 12795 points

    Over current protection is done by Short Circuit Protection. Please read chapter 7.4.4.4 for details.

    Once SCP is triggered, and if the option is latch on fault, IC will not restart.

  • 0 in reply to Ning Tan
    Expert 1440 points

    Hi Ning,

    Even if the CS threshold is 200mV, if it exceeds it for 8 consecutive cycles, the output short-circuit protection will be activated. I understood.

    Do you have any ACDC products that meet the following specifications?

    AC Input Specifications:

    • AC100V system: AC85 to AC138V
    • AC200V system: AC187 to AC276V

    DC Output Specifications:

    • DC12V
      • Steady: 2.0A
      • Peak: 2.5A

    Protection Functions:

    • Overcurrent protection: Auto retry
    • Overvoltage protection: Latch shutdown
    • Overheat protection: Latch shutdown

    Feedback:

    • Secondary side feedback

    Power Control:

    • Current mode (voltage mode not allowed)

    Best regards,

    Kyohei

     

  • 0 in reply to Kyohei
    TI__Genius 12795 points

    Kyohei,

    Can you please clarify why auto retry is desired when over current presents? Excessive period of over current may damage the power stage. 

    For UCC28750, the auto-retry time interval is in 10ms, depending on system design. Is this what you need? Or you just need a feature that ignores the over current for some period of time, say 1mS? 

    Best,

    Ning

  • 0 in reply to Ning Tan
    Expert 1440 points

    Hi Ning,

    Thank you for your reply.

    The reason for desiring auto-retry for overcurrent protection is to account for temporary inrush currents in the design.

    Therefore, a device that can recover from overcurrent protection with auto-retry, and can latch off for overvoltage protection and thermal protection, is required. The expected value of overcurrent is currently being confirmed with the customer.

    During short circuit protection, the value at the CS pin is determined by Rcs, but what is the maximum allowable value for Ipeak?

    Best regards,

  • 0 in reply to Kyohei
    TI__Genius 12795 points

    Kyohei,

    I assume the intention is to rely on auto-retry in power up phase. This will increase the start-up time quite bit. Please double check if there is requirement on start-up time. 

    The abs max of the CS voltage is 5.5V. So in theory, you can have max current = 5.5V /Rcs. I strongly suggest to leave enough margin for your design.

    Ning

  • 0 in reply to Ning Tan
    Expert 1440 points

    Hi Ning,

    I’ｍ currently confirming the start-up time with the customer, so please wait a moment.

    I understand the precautions regarding the value of Rcs.

    Is there a device that meets the customer's specifications, with automatic recovery for overcurrent protection, and latch shutdown for overvoltage protection and thermal protection?

    Best regards,

    Kyohei 

  • 0 in reply to Kyohei
    TI__Genius 12795 points

    Kyohei,

    You can consider UCC28630 for you need. Please keep in mind that it is a PSR, not SSR controller.