TPS23756: TPS23756 VC pin issue

user4206199

Part Number: TPS23756

customr evaluate TPS23756 encounter some issue of VC voltage when power on，detail as below picture，pls help provide some suggestion， SCH as attachedPOE SCH.pdf

over 5 years ago

0 user4206199 over 5 years ago

Intellectual 470 points

4745.POE SCH.pdf

0 Thomas Lewis over 5 years ago in reply to user4206199

TI__Expert 5615 points

user4206199,

Thank you for your consideration and/or adoption of PoE products from TI. This thread has been assigned to our PD Application Engineer - who happens to be on business travel for the first half of this week. He will review the attached schematic, and provide some guidance, ASAP.

Please excuse us if there is a longer cycle time than normal in this case. He will reply by the end of this week. If truly an urgent case, please let me know and I will do my best to reassign.

0 Darwin Fernandez over 5 years ago in reply to Thomas Lewis

TI__Mastermind 40120 points

Hi User,

The VC voltage will dip when the converter starts switching due to the gate cap of the primary FET.

What is the voltage rating of the 10uF cap? If too low, the DC bias will make the effective capacitance much lower. The cap should be increased to 22uF if the voltage is drooping too much such that the DCDC shutdowns.

Regards,

Darwin

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TPS23756: TPS23756 VC pin issue