What's the meaning of CTAT voltage, what's the relationship between CTAT voltage and temperature.
CTAT stand for complementary to absolute temperature. It is a bandgap reference that has a negative slope relative to temperature. This can be used with a reference that is PTAT (proportional to absolute temperature) to make a voltage that is constant with temperature, as long as the slope are summed and the slopes are complimentary.
For the AD9625, the junction temperature can be calculated from the voltage output on the VMON pin using this formula.
VMON (V) = −0.0013 × TEMP(C) + 0.8675