Hello I'm designing a temperature surveillance using LT2986.
According to the datasheet (Figure 8) a diode measurement can be done with a single channel or differential, using two channels.
Diode channel assignments follow the general conventionshown in Figure 8. The anode ties to CHD (where D isthe selected channel number) for both the single-endedand differential modes of operation, and the cathode isgrounded. For differential diode measurements, the cathodeis also tied to CHD-1
The text specifies that in both cases, Cathode has to be connected to GND (makes sens).
Thank you for your answer
Differential mode has two advantages for diodes:
1) If COM was tied to a different potential than GND for other sensors, using a differential reading for the diode ensures the voltage is sensed correctly.
2) If the ground connection between the LTC2986 and the diode had significant resistance and/or there were large ground currents - the ground potentials for the diode and the LTC2986 may differ. In that case, routing the diode signal differentially back to the LTC2986 would improve accuracy.
To stay with the 2-conversion mode I would suggest only adding a small capacitance (100pF - 10nF). You can add series resistance but you must then use the 3-reading mode. The diode ends up being a fairly low impedance source so I would say unless you have a lot of interference in your environment you could probably directly connect and be fine.