LTC2986 channel configuration

reb2121 on Feb 21, 2019

I'm looking through the LTC2986 datasheet and I'm a little bit confused about the external configuration for the single ended and differential thermistors.

If I understand correctly, the device has ten channels, but can only be connected to three thermistors in single-ended mode (each thermistor connects to one terminal and to COM; each independent sense resistor requires two channels).

In differential mode, it seems like it can handle four thermistors (two terminals each), plus a shared sense resistor (two terminals).

Can anyone please confirm or correct?

Thank you!

Top Replies

LoganC
Feb 27, 2019 +1 verified
HI reb2121 - that sounds right but I think we can get even more with Rsense sharing.

Rsense sharing uses an internal ground switch to provide a return path for the excitation current - in single-ended…

+1 LoganC

on Feb 27, 2019 4:49 PM
HI reb2121 - that sounds right but I think we can get even more with Rsense sharing.

Rsense sharing uses an internal ground switch to provide a return path for the excitation current - in single-ended mode that current is always forced to GND and there's no way to share an Rsense.

In differential mode with each thermistor "floating" only connected to the LTC2986 you can actually have 8 thermistors - they are all in series and each one gets grounded at measurement time and the differential voltage between channels is measured.

You will have to watch out for settling time as with 8 thermistors (esp. NTC at cold for example) the RC constant even with parasitic capacitance can be significant.

The best way to check configurations is via the demonstration software GUI - it has a configuration checker built-in and can also generate Linduino (Arduino) compatible C-code to jump-start your development. You can grab it here: https://www.analog.com/en/products/ltc2986.html#product-requirement

SE:

DIFF w/ shared Rsense:

Hope this helps!

-Logan
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