LM51561H-Q1: p-Tr on SS pin

Tosh+

Expert 7890 points

Part Number: LM51561H-Q1
Other Parts Discussed in Thread: LM5156

Hi Team,

I saw the reference design with LM5156 (PSR Flyback)

There is p-ch Tr from SS to COMP, what's the purpose? (discharging comp during soft start?)

What type/condition should we choose this Tr?

over 2 years ago

0 EM over 2 years ago

TI__Genius 11215 points

Hello,

Thanks for reaching out. Can you please share the reference design from which you took this screenshot?

Kind regards,
EM

0 Tosh+ over 2 years ago

TI__Expert 7890 points

PMP41005_Sch.pdf

+1 EM over 2 years ago in reply to Tosh+

TI__Genius 11215 points

Hi,

Thank you for your reply. The PNP bipolar transistor is to pull down the comp and therefore limit the duty cycle during start up. As anyway this answer was already given to you via email, I will now close the thread.

Kind regards,
EM

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LM51561H-Q1: p-Tr on SS pin