What is the tempco of the digital potentiometer?
There are two components that make up the resistance at any given setting, the switch resistance (wiper resistance, RW) and the pasive resistance (RS).
Together they add up such that
RWB = RS + RW
RS = RAB / 2N * D,
RAB is the nominal resistance
D is the decimal code
N is the resolution bits
The tempco of the passive resistor, which is published in the data sheet, is typically in the range of a few tens of ppm/°C for thin film or a few hundred ppm/°C for poly.
The resistance of the switch, on the other hand, doubles in 100°C. As a result, the overall tempco is nonlinear and it is worse off at low value codes where the switch resistance dominates.
Attached file shows a typical curve for a thinfilm resistor digital potentiometer, at lower codes the switch resistance becomes dominant. The inflection point where the passive resistor becomes dominant depends on the value of RS.
Users should refer to the tempco graphs in the data sheets for more detailed information
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