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UCC28610EVM-474: MOT Disable - High Power Consumption

Part Number: UCC28610EVM-474
Other Parts Discussed in Thread: UCC28610

We want to use the enable function on the UCC28610. We have experimented with shorting the MOT pin to ground, and indeed the converter shuts down. But the problem is, that on the 12V 2.1A eval board, the power consumed from 230V mains then increases to 0.75W, while one reason to disable this power supply would be to reduce power consumption to sub 30mW. The power supply will have a "sister" supply, of basically the same design, which will keep running. Maybe this can be used to provide the aux supply? Is there a solution to this high power consumption when disabled?

  • Hello,


    I reviewed the block diagram and figure 18 and 19.  If the on time is on for too long the MOT pin will cycle between 1 V and 3 V.  By pulling the MOT pin to ground you will stop the MOT pin from cycling and also prevent the over load timer from from resetting.  VDD will be cycling between VDDon and VDD off without switching the gate drive.  So it looks like charging and discharging the VDD capacitor is drawing too much current.  This agrees with what you had mentioned.

    The other option for shut down would be to pull the VGG pin to ground with an external FET.  In this way you will not dissipate any power by charging the VDD capacitor.

    Regards,