If you find that the value stored in the temperature register is not being explained by the equation in the datasheet:
Temperature Register = (AIN Register × TGAIN Register/16384) + (TOFF Register × 2).
The MAX77818 includes a thermistor curve adjustment register that updates the temperature calculation by the following recursive equation automatically if the value in the curve register (0xB9) is non-zero.
TEMP = TEMPx + TCURVE x (TEMP-0x1400) x (TEMP-0x1400)/0x40000 x if(Temp<0x1400,-1,1)