TMP05 Temperature Readings Having Large Offsets.

I am using the ADT7470 and the TMP05 in a daisy chain configuration and there are five sensors.

Temperature readings are not accurate and read a higher value than that measured by spot IR thermometer and a thermistor.

These readings are stable offsets and do not jump around but the temperature offsets are different to each device.


We have shipped approximately 750 units since 2012 with each unit having five TMP05. Some of these units have been in the field for more than 3.5 years and do not suffer from the above mentioned problem.


Note I did submit a similar question in 2012 where the temperature readings suddenly jump as high 100ºC and then return back to the normal expected temperature. These were observed in the initial prototype boards and were not present in production boards.


Please refer the attached documents for more details.


Block diagram = ADT7470_TMP05_Block_Diagram.pdf


Problem Report = Problem Report - ADI Enginnering Zone


Circuit diagram = ADT7470_TMP05_Daisy_Chain

(Note I have updated the diagrams since the 2012 post)


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