I am currently working with an MSP430BT5190 and I would like to use the internal temperature sensor from the ADC12 channel 10 for my product.
I am using the calibration values from the TLV table, waiting more than specified for REF supply to setup. The sample & hold time is superior to what is specified in the datasheet.
Everything is set correctly and most of the time I measure a consistent value. The problem is that when I do several consecutive conversions, some values are more than 5°C above the previous read values.
For example, I get the following sequence:
23.2, 23.4, 23.1, 23.2, 29.1, 23.2, 23.4, 32.1, 23.4, 25.7, 23.1
I thus have a problem of repeatability. Is there a known issue about the repeatability of this sensor or a known noise issue ? If yes, is there a known workaround, a dedicated application note?
The product I am working on is a medical device, and this value is used as a double check to know the correct operation of an external sensor, therefore the repeatability is a key issue.