UCC28780EVM-021: UCC28780

Jung-hui Cheng

Part Number: UCC28780EVM-021
Other Parts Discussed in Thread: UCC28781, UCC28780

Q2 (P/N BSS126H6327XTSA2) of UCC28780EVM-021 has drain-source on-state resistance around 300 ohms (maximum 700 ohms). Could use use CPC3960 which has maximum on-state resistance 40 ohms. Any problem on using an FET for Q2 with lower on-state resistance?

over 2 years ago

0 Adam E2E over 2 years ago

TI__Intellectual 2430 points

the Q2 is only clamping the voltage to let SWS pin sensing the voltage , not the main switching path , and the CPC3960 package is much bigger.

if they need the second source of BSS126 , they can refer the CPC3982 , and we also use it at UCC28781 EVM board , and same package with BSS126.

+1 Jung-hui Cheng over 2 years ago in reply to Adam E2E

Prodigy 150 points

The footprint of the new layout is for SOT223 package. The maximum on-resistance of CPC3982 is 380 ohms. Is lower on-resistance of CPC3960 OK?

+1 Adam E2E over 2 years ago in reply to Jung-hui Cheng

TI__Intellectual 2430 points

Hi,

Lower Ron-resistance is fine.

+1 Jung-hui Cheng over 2 years ago in reply to Adam E2E

Prodigy 150 points

REF pin of UCC28780 was damaged to low resistance twice under less than 50VDC input. EVM module is OK under 50VDC input. Do you have idea what would cause the damage as REF only used in closed-loop control.

0 Adam E2E over 2 years ago in reply to Jung-hui Cheng

TI__Intellectual 2430 points

for the startup issue , you can refer the app note as below link.

app note : www.ti.com/lit/pdf/slua982

Power management

Power management forum

UCC28780EVM-021: UCC28780