PMP10468: determine resistor devider from the VS pin

sterie

Part Number: PMP10468
Other Parts Discussed in Thread: PMP10276, UCC28700

Hi,

i have tried to determine the resistor devider from the VS pin as in the design PMP10276 RevB. But i can´t get the values for the R4 = 75k.

As i follow the datasheet UCC28700 equation (1): RS1 = R4 = VIN(run) x sqrt(2) / ( NPA x IVSL(run) ) = 85V x sqrt(2) / ( 3.64 x 220µA ) = 150k

But in the design you use 75k, is this with a safety factor? 220µA x 2? So it would be 75k i think?

Regards

Stefan

over 6 years ago

0 Peter Meaney over 6 years ago

TI__Mastermind 31580 points

Hi Sterie,

Thanks for your interest in TI's products, I have contacted one of our engineers who will respond to your post.

Regards

Peter

0 sterie over 6 years ago in reply to Peter Meaney

Intellectual 340 points

Hi Peter,

can you please also ask for the used VOCC (target lowest converter output voltage in constant-current regulation) in the design PMP10276 RevB.?

Because i also can not get the right value for NAS = ( VDD(off) + VFA ) / ( VOCC + VF ), according to datasheet UCC28700 equation (26)

Or is there a example calculation for this available?

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PMP10468: determine resistor devider from the VS pin