DCAP mode minimum ripple injection

Anyone can help on this?

I would use the recommended value.  Any reason why you want to use less ripple?

John,

Thanks for reply. My customer just needs to use the minimum injection ripple to achieve very accurate output voltage based on all test going well.

Reading thru the datasheet and app note, it looks like this is somewhat complicated.  There are three components to consider: the effect on DC output voltage, the effect on loop stability and the effect on jitter performance.  I would suggest that the third criteria is the most important.  For your customer, the effect on DC offset can be calculated and taken into account.  The datasheet shows how to set the feed back resistors taking into account the ripple injection.  If you use an SP cap for the output,  you can avoid all this and just use the ESR of the output cap to generate the required ripple content.

If you need additional clarification, I suggest you contact the authors of the app note directly.  They may have some experimental data to back up their app note.

Nancy,

Thanks for reply.

10~15mV is the ripple value of ripple injection circuit. How about the total ripple injected into FB pin (VFB_ripple)? Actually, this ripple is valid for D-CAP mode. Do you have this FB pin minimum ripple caculation result or experiment test result?

Thanks.

Nancy,

Thanks for reply. I know that the FB pin ripple is around 21mV, but do you have some anylisis or test result on the minimum value of this ripple?

Thanks.

Nancy,

Got it. Thanks for your time.