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UC2844: Protection issue of UC2844

Jason Fan
Intellectual 1705 points
Part Number: UC2844
Other Parts Discussed in Thread: UCC2804

Hi  Experts:

customer designed the flyback with the two isolated output by UC2844.  One is 15V for the UC2844 power supply and the another is 24V  for the system power, 

The feedback is on the 24V rail.

When shorting the 24V,  the UC2844 will enter the cycle by cycle current limiting mode constantly , it will make the Mosfet damaging because the chip has no hiccup mode which will latch the driver for a long time. So customer has to change the design due to this issue .

Could you please recommend a new chip with the hiccup mode or the aux winding voltage monitor  to protect the over current case,   and should  only change a little in the current design ?  

Thanks!

  • 0
    TI__Genius 13660 points

    Hi Jason,

    I found that UCC2804 may meet your requirement.

    UCCx80x have the same pin configuration as the UCx84x family, and also offer the added features of internal full-cycle soft start and internal leading-edge blanking of the current-sense input.

    The UCCx80x current sense input connects to two comparators: the PWM comparator and the overcurrent comparator.  

    But please note that it cannot be pin-to-pin to replace UC2844 directly on the UC2844 board due to different  range of VCC voltage and so on.

    Regards,

    Teng