NTC Probe Wiring for LTC2984
Whats the max number of 2 wire probes NTC i can hook up to LTC2984ILX#PBF? How do I wire up custom 2 wire NTC probe: They need 2.5VDC and they read 110 K Ohms - 17.65k ohms based on tempature. I think i want Pseudo-Shared?
Thought for 2 mins 18 sec
I can give you the wiring concept, but I can’t verify the exact max probe count from the files I can access here because the indexed results only surfaced general datasheet-handling guidance, not the actual LTC2984ILX#PBF thermistor pages. For this kind of question, the datasheet needs to be the source of truth, and missing/ambiguous datasheet details should not be guessed
Short version:
- Yes, pseudo-shared is probably the right topology if you want multiple 2-wire NTC thermistor probes with one shared reference path.
- Your probe does not sound like something that should be driven with a fixed 2.5 VDC directly. The chip normally measures thermistors by forcing a known excitation current and measuring the resulting voltage ratio against a precision sense Generic Resistor, not by applying a constant voltage.
- So if “needs 2.5 VDC” means the sensor must be biased from a stiff 2.5 V source to work, that is a red flag. If it’s just a passive NTC whose resistance is 110 kΩ to 17.65 kΩ, then it should be usable as a custom thermistor entry.
What I’d do electrically:
- One side of each 2-wire probe to a dedicated analog input.
- The other side of each probe to the common return/sense path used by the pseudo-shared configuration.
- Use one precision sense Generic Resistor for the group, with short, clean routing.
- In software/config:
- select custom thermistor
- enter either the resistance table or the Beta/Steinhart-Hart data
- select 2-wire
- select pseudo-shared if you are sharing the reference path among several probes
About the max number:
- I would not trust a guess here.
- It depends on how LTC2984ILX#PBF allocates analog inputs for:
- thermistor nodes
- shared sense node
- any extra return/reference channel in pseudo-shared mode
- So the real answer is determined by the datasheet’s channel-allocation diagram, not just “20 inputs”.
For your resistance range:
- 110 kΩ to 17.65 kΩ is a perfectly plausible custom NTC span.
- Pick the sense Generic Resistor in the same ballpark as the middle of the thermistor’s operating range for best ADC utilization.
- A fixed 2.5 V divider-style hookup is usually not the preferred way with this chip.
If you want, send me either:
- the thermistor’s resistance table / Beta value / R25 value, or
- a screenshot of the exact pseudo-shared page from the datasheet,
and I’ll tell you:
- the exact max probe count,
- the exact pin wiring, and
- a good starting value for the shared sense Generic Resistor.
