MSP430FR2355: Internal connection of SAC

Conor

Guru 12875 points

Part Number: MSP430FR2355

Hi,

I have a question about the SAC module built into the MSP430FR2355.

(1) Is it possible to use the SAC module as a "constant current source" in General Purpose mode?

　Specifically, I want to output 600 μA.

(2) Is the output of SAC1 directly connected to the ADC (without going through a comparator)?

　 From the data sheet "6.10.17 Cross-Chip Interconnection (SACx are MSP430FR235x Devices Only)", SAC1 and SAC0 appear to be connected to the ADC via a comparator.

　In other words, is the following circuit configuration possible?

Thanks,

Koki

over 4 years ago

0 Leonardo Estevez over 4 years ago

TI__Genius 12615 points

Hi Koki,

This document provides some more details on how to configure the SACs in different modes:

https://www.ti.com/lit/an/slaa833a/slaa833a.pdf

For your first question, DAC mode should provide the configuration you are looking for. (section 2.5)

For your 2nd question, yes, the output of SAC0 and SAC1 can be internally connected to an ADC, for the other two SACs, an external wire has to be connected to an ADC capable pin.

BR,
Leo

0 Conor over 4 years ago in reply to Leonardo Estevez

Guru 12875 points

Hi, Leo

Leonardo Estevez said:
For your first question, DAC mode should provide the configuration you are looking for. (section 2.5)

Is it okay to recognize that DAC cannot be used when using "General Purpose mode"?

Is DAC available in SAC only in DAC Mode or Inverting PGA Mode?

Thanks,

Koki

0 Leonardo Estevez over 4 years ago in reply to Conor

TI__Genius 12615 points

Hi Koki,

The mode is a description of the register settings for each MUX. If you have the PSEL register set to take input from the DAC, it can't also be taking input from a pin. You can configure the PSEL and NSEL registers directly. When the document refers to General Purpose mode, it is referring to a configuration in which both the negative and positive inputs are connected to an external pin.

BR,
Leo

0 Conor over 4 years ago in reply to Leonardo Estevez

Guru 12875 points

Hi, Leo

1.General Purpose Mode

2. Buffer Mode

3. Non-exposed PGA Mode

4. Inverting PGA Mode

5.DAC Mode

I understand that the PSEL in yellow selects the DAC.

Also there are 5 modes in the SAC module.

Therefore, among 1 to 5, only 2, 4.5 can use DAC in SACx.

Is this perception correct?

If so, I can't use the DAC in "General Purpose mode", right?

Thanks,

Koki

0 Leonardo Estevez over 4 years ago in reply to Conor

TI__Genius 12615 points

Hi Koki,

Yes, that's correct.

BR,
Leo

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MSP430FR2355: Internal connection of SAC