Voltage reference temperature coefficient is a measure of the change in reference output voltage with a change in temperature. The temperature coefficient defines the maximum voltage variation over a given temperature range. The temperature coefficient is calculated using the box method.The box method uses a minimum and maximum temperature and measures the reference voltage at those two temperatures. The formula is shown below..
Temperature Coefficient = (VREFmax - VREFmin) / (VREFnom * Temperature Range) * 1000000
VREFmax and VREFmin are the maximum and minimum reference voltages measured at the two temperature extremes
VREFnom is the nomimal reference voltage
Temperature Range is the difference between Tmax and Tmin