ADT7461: Input resistance vs temperature error

Document created by analog-archivist Employee on Feb 23, 2016
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The leakage resistance of the diode pins of the ASIC could be 2M ohm worst
case, @120 C. Does this mean the temperature reading could have an error of 30
C? (Using figure4, rev0 page 7of 24, ADT7461 datasheet).
Please let me know whether I am interpreting the data correcly or not and any
possible solution.

 

The graph you are looking at in the data sheet is temperature error vs. PCB
leakage resistance.
This test is done by tying resistors values to the D+ pin to Vcc, or to the D-
to Gnd, and measuring the temperature error.

You ask about 2 MOhm worst case on the diode ASIC pins.
If the resistance is evenly matched, their effect on the temperature
measurement cancels out, so normally, there is very little error due to leakage
resistance.
However, if there is only leakage resistance on **one** of the pins ( unlikely,
I think), then you would be correct.

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