UCC28740: UCC28740 start up

Skylar Li

Part Number: UCC28740

Hi Experts,

In order to start UCC28740, should both VDD pin and HV be connected? If yes, what should the minimum value of V(hv) be? Thank you!

over 1 year ago

0 Harish Ramakrishnan5 over 1 year ago

TI__Mastermind 19455 points

Hi Skylar,

Thank you for the query on UCC28740.

In short, yes both VDD and HV have to be connected. Minimum recommended voltage at HV pin to have reliable startup is atleast 30V.

Regards,

Harish

0 Skylar Li over 1 year ago in reply to Harish Ramakrishnan5

TI__Intellectual 760 points

Hi Harish,

Thanks for your prompt reply! There is a another question about the datasheet. The bias-supply operating voltage of VDD is from 9V-35V but VDD turnon threshold is 21V. I wonder that if VDD=18V and V(HV)=390VDC, will UCC28740 start up? Thank you!

Regards,

Skylar

0 Harish Ramakrishnan5 over 1 year ago in reply to Skylar Li

TI__Mastermind 19455 points

Hi Skylar,

Thank you for the query.

There should be no concerns to start up ucc28740 at the above conditions. VDD will cycle between turn on threshold of 21V and 8V during HV startup and fault conditions. But once the auxiliary winding is up, that voltage must lie between 8-35V for normal operation. Please let me know if you have additional questions.

Regards,

Harish

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UCC28740: UCC28740 start up