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UCC28722: UCC28722 Power on Issue

Part Number: UCC28722

Dear Sir/Ms.

The following are the problems encountered by the customer UCC28722 during testing.

Input DC24V Output DC23V Power 20W
When the power is turned on, the output voltage is abnormal, and a triangle wave between 21V and 7.6V will appear in the VDD  . DRV will send 3 pulse signals when VDD reaches 21V.

Can you suggest a solution?

Best Regards,

Kami HuangUCC28722_sch.pdf

  • Kami

    From your description it sounds like a fault condition is being triggered in UCC28722.  The startup operation that you describe is identical to the startup operation explained in section 7.4.4 Start-Up Operation (page 14) of the UCC28722 datasheet.  If a fault condition is measured after the 3 pulses, UCC28722 will enter a fault shutdown, and attempt to restart after VDD voltage discharges below UVLO threshold. 

    Details about these fault conditions are in section 7.4.5 Fault Protection (page 15) of the UCC28722 datasheet.  What we recommend is that you measure the voltages on UCC28722 pins during startup to see if any fault condition is triggered.  We have the following app note that goes into more details about debugging techniques http://www.ti.com/lit/an/slua783/slua783.pdf

    Best Regards,

    Eric