TPS61391: Clarification of R_protect (again)

Andrea Ronco

Part Number: TPS61391

Tool/software:

Hi,

Sorry to come back to this again, I accepted the previous answer without checking.

Contrary to what stated in the previous answer, R_protect is clearly right there in the official evaluation board, numbered R3.

So again, what is the purpose of this resistor?

Best regards

6 months ago

0 Shipeng Cheng 6 months ago

TI__Genius 17250 points

Hi,

Travis will reply to you tomorrow. Thanks.

0 Travis Wang 6 months ago in reply to Shipeng Cheng

TI__Expert 8695 points

Hi Andrea,

R3 is Rfilter instead of Rprotect. Rprotect is still not necessary.

Best Regards,

Travis

0 Andrea Ronco 6 months ago in reply to Travis Wang

Prodigy 80 points

Hi Travis,

You are right, in my design I have R_filter, but I confused it with R_protect.
Then R3 has nothing to do with the APD monitor, it's just used to reduce the output ripple of the device, correct?

Thank you for the fast reply.

Best,
Andrea

+1 Travis Wang 6 months ago in reply to Andrea Ronco

TI__Expert 8695 points

Hi Andrea,

MONIN pin powers the current mirror. So R3 and C9 are filter that stabilizes this power rail on the internal current mirror. Noise on this rail may couple to the current mirror gate and affect accuracy.

But this filter only reduces ripple on MONIN pin and does not affect ripple on boost Vout

Best Regards,

Travis

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TPS61391: Clarification of R_protect (again)