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UCC256304: IC power loss at FB terminal low shutdown

Hiroshi Doi35
Expert 2845 points
Part Number: UCC256304

Hi all,

My customer request is IC power loss should be less than 5mW  at FB terminal Lo.

  The condition is,  AC230V  and  Vcc = 20Vmax.  FB terminal is GND level.

How about UCC256304 power loss max.?

  • 0
    TI__Mastermind 27145 points

    Hi Hiroshi-san,

    Thanks for your interest in UCC256304. If FB is held low for an extended period of time, the controller will not switch. This means that VCC will not be replenished form the bias winding. The result is when the VCC voltage falls below 10.5V, the controller will re-enable the HV startup circuit to charge up the VCC pin.

    The maximum leakage of the HV pin is ~7.55uA. Assuming the voltage at the HV pin is the average of the rectified line, this gives 2*sqrt(2)*230V*7.55uA/pi=1.6mW. This number does not include when the HV startup circuit is active however. The actual average power consumption of the IC will depend on how frequently the IC enables the HV startup circuit to charge up VCC which is dependent on the VCC voltage and how much capacitance is on the VCC pin.

    Best Regards,
    Ben Lough