The ADS1291, ADS1292, and ADS1292R contain an on-chip temperature sensor. This sensor uses two internal diodes with one diode having a current density 16x that of the other, as shown in Figure 19. The difference in diode current densities yields a difference in voltage that is proportional to absolute temperature.
As a result of the low thermal resistance of the package to the printed circuit board (PCB), the internal device temperature tracks the PCB temperature closely. Note that self-heating of the ADS1291, ADS1292, and ADS1292R causes a higher reading than the temperature of the surrounding PCB.
The scale factor of Equation 3 converts the temperature reading to °C. Before using this equation, the temperature reading code must first be scaled to μV.