Decoupling Capacitance

Abundis DelaO15

Other Parts Discussed in Thread: MSP430FR5739

Hi,

I am working with an MSP430FR5739, and I would like to know where I can find the values for the decoupling capacitance and if it is possible to reduce it?

over 9 years ago

0 Dennis Eichmann over 9 years ago

Guru 74080 points

Hi Albert!

I'm not aware of a document showing the minimum required decoupling capacitor values. Having 100n in parallel with 10µ connected to the supply pins is a good value you can work with. Only in the ADC10 section of the User's Guide you can find a recommendation - it also lists those two values for DVcc and AVcc in order to minimize noise coming from the supply rails when using the ADC module. So when not using it, you can of course lower the capacitance value and also use only one, but this also depends on the rest of your circuit like the distance to the supply of your board. Hard to give an exact answer here.

Dennis

0 Ryan Brown1 over 9 years ago

TI__Guru**** 218157 points

Hi Albert,

Recommended decoupling capacitance is 10 uF + 100 nF as shown in Figure 16-11 of the User's Guide (SLAU272) and Figure B-30 of the Hardware Tools User's Guide (SLAU278). Section 5.3 of the device Datasheet (SLAS639) notes that the capacitor ratio of VCC to VCORE (CVCC/CVCORE) is 10, and since the capacitance required at VCORE is 470 nF the smallest VCC decoupling capacitance allowed is 4.7 uF, however you should be wary of the capacitor's tolerances as they could put your system out-of-spec.

Regards,
Ryan

0 Dennis Eichmann over 9 years ago in reply to Ryan Brown1

Guru 74080 points

Ryan Brown1 said:
Section 5.3 of the device Datasheet (SLAS639) notes that the capacitor ratio of VCC to VCORE (CVCC/CVCORE) is 10, and since the capacitance required at VCORE is 470 nF the smallest VCC decoupling capacitance allowed is 4.7 uF

Good point!

0 Abundis DelaO15 over 9 years ago in reply to Ryan Brown1

Intellectual 560 points

Thanks a lot for your answer!!

0 Abundis DelaO15 over 9 years ago in reply to Ryan Brown1

Intellectual 560 points

Sorry again,

Do you know where I can find the layout to identify which capacitors I can remove to reduce the capacitance? I've been looking at slau272c but I did not find anything. I don't know the capacitance of each element of the target (I'm using EXP-MSP430fr5739). Next to the microcontroller there are 3 capacitors, C14, C19 and C18.