LM27761: about datasheet figure

Yuya Mitamura

Part Number: LM27761

Why is 5.5Vin ripple voltage larger than 3Vin at Figure1 ? also please let me know about cause of increasing ripple at light load.

And I want to see PSRR-Frequency graph.

Regards

over 7 years ago

0 Chris Glaser over 7 years ago

TI__Guru**** 150880 points

Hi Mitamura-san,

The ripple is higher because there is more switching ripple at higher Vins. Assuming the LDO's PSRR is the same for the different Vins, this gives a larger output ripple. As well, this IC has a power save mode at light loads which increases ripple to provide better efficiency.

What is your Vin, Vout, and Iout needed? What are you powering?

0 Yuya Mitamura over 7 years ago in reply to Chris Glaser

Prodigy 30 points

Mr.Glaser

Thank you for answer
Vout=-3V,Vin=5V,Iout=100mA
Could you provide PSRR graph?
Regards

0 Chris Glaser over 7 years ago in reply to Yuya Mitamura

TI__Guru**** 150880 points

Generally, specific data like this is best taken by the customer on their exact board/design. What is the PSRR graph needed for? Do you have a specific noise target you need to meet or ripple that needs to be rejected?

0 Yuya Mitamura over 7 years ago in reply to Chris Glaser

Prodigy 30 points

We will discuss with customer.
Thank you.

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LM27761: about datasheet figure