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MSP430FR5738: Battery voltage measurement using VREF and ADC

Ali Aljumaili
Prodigy 250 points
Part Number: MSP430FR5738
Other Parts Discussed in Thread: TIDA-00468

Hi,

I have an application where I am using a 3.6V battery and a 2V LDO that is sourcing the MCU (MSP430FR5738RGE) and the rest of the circuit.

According to slaa828.pdf it is possible to monitor the power without using any external circuitry. My question is it possible to monitor the 3.6V raw battery voltage without any external circuitry? What will the internal voltage reference need to be set to? and how will the connection be? Any possible reference design you can recommend?

I have seen the TIDA-00468 reference design but still not 100% sure of the connection. 


Thanks in advance.

  • 0
    TI__Genius 17960 points
    Hi Ali,
    the direct battery voltage measurement without external components unfortunately does not work in your case.
    The method would be the following, but it works only with direct supply of the MSP430 from battery:
    With the MSP430 FRAM devices, which are equipped with an ADC on chip, to measure the supply voltage, you flip the role of reference voltage and measured voltage, means you select the power supply (battery voltage) as reference and apply the reference voltage of the integrated reference as input voltage. As the level of the built-in reference is known, you can calculate the supply = battery voltage.
    Now this is only possible if supplying the MSP430 directly from the battery. In your case, the battery voltage is significantly higher, thus you cannot apply it directly to any pins of the MSP430 device, as this would violate the specification.
    You can only apply a divided down portion of the battery voltage, but this of course requires external components (resistive divider and C at the ADC input, as to limit the battery discharge through the divider, it has to be of very high values. The C is to backup the to be measured voltage).

    Best regards
    Peter

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