LM3697: Output capacitor value

Roy Chou1

Part Number: LM3697

Hi Team,

As datasheet said, we suggest output cap > 0.4uF when consider DC derating. I'm not sure the reason of value. May you let me know the formula for the value?

To my understand, the output cap is for output voltage boost from LM3697. I used LP8866, but we place 10uF level cap as output cap. I have no idea why LM3697 output cap = 1uF is enough. And how can we define the 0.4V when we consider the DC detrating.

Regards,

Roy

over 3 years ago

0 Patrick Yao over 3 years ago

TI__Mastermind 36910 points

Hi Roy,

1. On our EVM this capacitor is 1uF. And this capacitance is determined by output voltage ripple.

2. For derating, you need to find the datasheet of the capacitor you used. In datasheet there should be a figure to show the real capacitance under different voltage. And the capacitance under your output voltage should be larger than 0.4uF.

Patrick Yao

0 Patrick Yao over 3 years ago

TI__Mastermind 36910 points

Hi Roy,

Do you have more questions? If not, I'll close this case later.

Patrick

+1 Patrick Yao over 3 years ago

TI__Mastermind 36910 points

Hi Roy,

I'll close this thread due to inactivity and if you have more questions, please reply to it directly and it will open again.

Please help to click "Resolve" if the problem is solved.

Patrick

Power management

Power management forum

LM3697: Output capacitor value