TPS61021A: Low R2

Kazuhiko Hirano

Part Number: TPS61021A

Hello,

My customer needs to use resistance of +/-0.1% accuracy for R1 and R2 to get required Vout accuracy.
But, for resistance of +/-0.1% accuracy, the selectable resister range is =< 100Kohms.
So, to get Vout=3.9V, they selected R2=24kohms + 1.6kohms and R1=100Kohms.
R2=25.6kohms is lower than the WeBench recommended value 100Kohms.
Though datasheet says “Changing R2 towards a lower value increases the immunity against noise injection.”, R2=25.6kohms could increase the immunity against noise injection?
Could you explain more details about this, please?

Best regards,

K.Hirano

over 2 years ago

0 Wenhao Wu over 2 years ago

TI__Genius 9046 points

Hi Sir,

Please consider this application note for how resistance of feedback resistors are influencing noise rejection. Thanks!

-Wenhao

0 Kazuhiko Hirano over 2 years ago in reply to Wenhao Wu

TI__Genius 11613 points

Wenhao

Thank you for your response.
Let me confirm one more.
Does “Changing R2 towards a lower value increases the immunity against noise injection.” mean the lower R2 the more immune to noise injection? In other words, the lower R2, the better immunity against noise injection?

Best regards,

K.Hirano

+1 Wenhao Wu over 2 years ago in reply to Kazuhiko Hirano

TI__Genius 9046 points

Hi Hirano,

Yes, you understanding is correct. Please note the Iq will increase as your feedback resistors are smaller.

-Wenhao

0 Kazuhiko Hirano over 2 years ago in reply to Wenhao Wu

TI__Genius 11613 points

Wenhao,

So, do you think R2=24kohms + 1.6kohms and R1=100Kohms are OK and no concerns?

Best regards,

K.Hirano

0 Kazuhiko Hirano over 2 years ago in reply to Kazuhiko Hirano

TI__Genius 11613 points

Wenhao,

Sorry, I overlooked your previous comments.
You already suggested Iq increase.
I close this thread, thank you for your support.

Best regards,

K.Hirano

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TPS61021A: Low R2