LM22670: DCM operation

Kuramochi Tadahiko

Part Number: LM22670

Hi,

Follows are described on "8.2.1.2.2 Inductor" of the datasheet;

"To keep the application in continuous conduction mode (CCM), the maximum ripple current, IRIPPLE, should be less than twice the minimum load current".

Does this mean that LM22670 can not work as DCM mode?

Best Regards,

Kuramochi

over 6 years ago

0 Juan Paulo Fung over 6 years ago

TI__Expert 3840 points

Hi,

The statement is referring to the opposite, that is, you don't want to be operating in DCM all of the time by poorly selecting an inductor value that will give you excessive ripple and won't let you operate in CCM. The next sentence in the datasheet clarifies that point by stating:

"The general rule of keeping the inductor current peak-to-peak ripple around 30% of the nominal output current is a good compromise between excessive output voltage ripple and excessive component size and cost."

Best Regards,
-JP

0 Kuramochi Tadahiko over 6 years ago in reply to Juan Paulo Fung

Guru 28715 points

Juan-san,

Thank you for your quick response!

I understood that this is general theory and it is no problem to operate LM22670 on no load.

Best Regards,
Kuramochi

0 Kuramochi Tadahiko over 6 years ago in reply to Kuramochi Tadahiko

Guru 28715 points

I correct above comment.

Minimum load of LM22670 is about 5mA as below.

Power management

Power management forum

LM22670: DCM operation