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MSP430FR5964: Options to monitor the supply voltage of the MSP430FR5964

Part Number: MSP430FR5964
Other Parts Discussed in Thread: MSP430F2618

Hello everybody,

my MSP430FR5964 runs at 2.8 V.

Now I am looking for a way to trigger an interrupt if the supply voltage VCC falls below 2.5 or 2.0 V.

With the MSP430F2618 you had the SVS module and could set the desired voltage.

Unfortunately I cannot set a threshold voltage for the SVS module on the MSP430FR5964.

Then I read that it is possible to use the COMP_E module for this.

As input voltage Vcc and as reference, a voltage from the internal reference module, e.g. 2.0V.

I don't understand here how the reference voltage is kept at 2V while Vcc drops below 2V ?

Or is there a simpler solution to monitor the supply voltage?

I am grateful for any help.

  • Hello Krams,

    As for the Reference voltage, I agree that you can't have the reference voltage be higher than VCC.  Section 8.12.10.1 gives the specs for the built in Reference, and AVcc(min) show that for 2.0V reference you need a minimum of 2.2V VCC.  See below.  

    So, I don't see how you can monitor VCC with the comparator directly.  My only thought is that you could add an external resistor divider from VCC to the comparator input.  For example, you could divide VCC/2 and then compare it vs 1.2V to detect vs 2.4V.  You can't really adjust it via software, would basically be set by your divider.  

    This isn't perfect, as resistor divider will constantly draw current, so I would make the resistors rather large to try and mitigate.  

    Let me know if this is a solution you could implement.  

    Thanks,

    JD

  • You may want to try the so-called "battery monitor" signal which generates AVCC/2 and feeds it into ADC channel 31. The (internal) divider means the max signal would be 1.65V. You could run the ADC slowly/continuously with the Window Comparator enabled to watch it. You'd still have to do a bit of a dance as AVCC fell through 2.2V.

    The User Guide is somewhat skimpy on description, but it shows up in UG (SLAU367P) Sec 34.1 and Fig 34-1, as well as data sheet (SLASE54C) Table 5-28. The keyword is ADC12BATMAP.