Do you have to always connect analog supply to MSP430 board?

[jenda]

Hi

I have two independent 3V supplies on an MSP430 board. DVCC for the digital and AVCC for the analog part. The MSP430 exposes a separate pin for the analog supply (analog part of the ADC and DAC).

May I only power the digital part of the MSP430 by applying 3V to DVCC and 0V to AVCC or will this damage something?

I can not get this information from the datasheet since AVCC and DVCC are always tied together.

Thank you for your help!

Cheers, jenda

 

[bmwcoupe]

msp430 avcc dvcc

Hi
I Connected the two pins to VDD 3.5V
all works ok, and this is the way it should be done...
ADC tested ok, and all works fine...

 

[kender]

msp430 avcc

If you want to to have a more quiet analog supply (less noise), you can add an RC or LC filter between system Vcc and uC's AVcc.

 

[jenda]

msp430 supply filter

This is what TI answered:

Please be aware that AVcc and DVcc are connected internally through a diode.The difference between those two supply voltages should not be bigger than 0.3V. Unfortunately this requirement is not included into all datasheets of MSP430 family - but applies to the whole MSP430 family. Please find information included at e.g.:

https://focus.ti.com/lit/ds/symlink/msp430f2370.pdf, page 17, Note1:

1. It is recommended to power AVCC and DVCC from the same source. A maximum difference of 0.3 V between AVCC and DVCC can be tolerated during power-up and operation.

Even if you turn off the analog interfaces e.g. ADC, you will still have to supply Avcc. In case you will not use the ADC at all you will have to connect Avcc to Dvcc