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MSP430FR5994: MSP430FR5994: ADC Temperture Sensor Sampling time

Mike52327
Intellectual 460 points

Part Number: MSP430FR5994

 

Hello, 

Looking into usign the internal temperature sensor of the MSP430FR5994 in our project, but I noticed that the minimum sampling time for the internal temp sensor is specified as 30 micro seconds in the data sheet. It also specifies that this includes a t_sensor_on time.

Is there a way to leave the sensor on so we can reduce the runtime sampling time of the temperature sensor? And if so, does anyone know where this t_sensor_on time is documented?  Could not find in the data sheet...

We have a timer->DMA->ADC->DMA sequnce that runs at a rate that will not work with a 30 microsecond sample time.  Our Conversion sequence is 10 or so channels, and that one channel would force all to be sampled with the same sampling time...

If not, will look to see if we can maybe interleave ADC sequences to minimize how often we sample the sensor...  I realize temp will not change often...  just looking for the least complex way to code such...

Thanks,

-mike

 

  • 0
    TI__Genius 13955 points

    Hi Mike,

    As for keeping the sensor on between conversions, eet REFON = 1 in REFCTL0 and leave it set. With the reference held on continuously, the sensor stays warm and the power-on portion of the 30 µs penalty does not repeat on subsequent reads.

    Regarding t_sensor_on — it is not listed separately in the datasheet. It is folded into the 30 µs minimum sampling time in the ADC12 Electrical Characteristics table.

    As for sample temperature less often, since temperature changes slowly, sampling it every 100–1000ms from a separate slow timer is perfectly fine and simplest to implement.

    Hope this helps!

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