REG1 DC/DC decoupling

[rsend]

Hi,

We are running an application using REG1 only in DC/DC mode, REG0 is disabled. I believe we've found a small issue with our decoupling of all the power pins, but I'm not sure which pins actually go to what rail so I wanted to check in here.

Our current decoupling is as follows:

- DEC3 - 100pF

- DEC2 - none

- DEC5 - none

- DEC6 - connected to DEC4, connected to DCC output (after the inductors), decoupled with 1uF, 47nF and 10pF

Question: Should DEC2 and DEC5 also have their own decoupling capacitors? We have them in our schematic (0.1uF) but they're currently marked as no-load. This schematic was done a while back and I don't recall / have records as to why this might have been intentional.

In looking at the reference schematic configuration 5 in Product Spec v1.0 there is an 820pF capacitor on DEC5.

Cheers,

R

[Simonr]

Hi Rafael

You are correct. DEC5 should have an 820pF decoupling capacitor as well. Additionally, the 10pF on DEC6 should be not connected according to the reference design. You did not mention DEC1 either, this should be 100nF.

Best regards,

Simon

[JHiggins]

Hi Simon, 

820pF is a bit of an odd value.  Is 1nF acceptable?  What might be the impact of using 1nF instead of 820pF?

Thanks,

Jasen

[Simonr]

Hi Jasen

We haven't characterized the IC with 1nF, so we can't guarantee that this is OK, but I assume it would work. Anyways, we do recommend using 820pF, as we know for a fact that those work.

Best regards,

Simon