MSP430FR2512: May I Leave VREG Unconnected?

Jay09

Part Number: MSP430FR2512

I am finishing a layout for a MSP430FR2512IRHLR. If I don't plan to use the output from VREG, is there any reason I can't leave VREG unconnected? I saw in a reference schematic that one design connects it to a 1uF X5R capacitor to ground and wanted to check what the impact if any of leaving it unconnected would be.

Thanks!

over 5 years ago

0 Eddie LaCost over 5 years ago

TI__Mastermind 45085 points

John,

VREG is the internal regulator which is used to supply the cap touch pins. See table 4-1 of the datasheet. You need to have that decoupling capacitor or the regulator will be unstable.

https://www.ti.com/lit/ds/symlink/msp430fr2512.pdf

0 Jay09 over 5 years ago in reply to Eddie LaCost

Expert 1030 points

Hi Eddit,

Thanks for this answer. In the design I am referencing VREG is just connected to a cap to ground. The net "VREG" as pictured in this diagram doesn't appear to be used anywhere else -- the marker appears to be just there for clarity.

So is the change to just to add a capacitor to ground (joined with the other caps to ground of DVCC?)

Here's the schematic I am referencing.

0 Jay09 over 5 years ago in reply to Jay09

Expert 1030 points

To close the loop, here is my final layout, after factoring in your advise --- would you mind taking a look?

0 Eddie LaCost over 5 years ago in reply to Jay09

TI__Mastermind 45085 points

VREG is used internally, but does require the 1uF decoupling capacitor external. This is why you do not see VREG connected anywhere else on the schematic.

In your schematic, VREG is connected to a 100nF cap(C25). This cap needs to be 1uF.

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MSP430FR2512: May I Leave VREG Unconnected?