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UCC28740: Duty and Switching Frequency will Reduce Under Heavy Load Condition

Francis Jiang

Expert 3310 points

Part Number: UCC28740

Tool/software:

Hi Team,

Customer feedback that UCC28740's duty and switching frequency will reduce under heavy load condition, during this time, it can be tested that CS pin voltage is 0.936V~1.1V, exceed the Vcstmax. Would like to check with you whether this is a normal behavior? And could you please help explain it to customer more clear? Thanks.

BRs

Francis

0 Ning Tan 6 months ago

TI__Genius 12795 points

Francis,

The freq should increase as the load increases. Please see the control law in datasheet.

Do you have any waveform or schematic to share?

Thanks,

Ning

0 Francis Jiang 6 months ago in reply to Ning Tan

TI__Expert 3310 points

Hi Ning,

The waveform are shown as below:

CH1: DC bus, CH3: DRV, CH4: CS, CH5: 48V Output, CH6:Vdd

Zoom in, CS voltage is 0.936V~1.1V

Could you please help check it again? Thanks a lot.

BRs,

Francis

0 Ning Tan 6 months ago in reply to Francis Jiang

TI__Genius 12795 points

Francis,

The waveform is not clear either. Can we work on this offline?

Best,

Ning