The variation in V_REF over temperature is defined by its temperature coefficient (TC, also referred to as temperature drift) which has units of ppm per degree Celsius (ppm/^oC). The temperature coefficient can be specified over several different temperature ranges, including the commercial temperature range (0 to 70^oC), the industrial temperature range (-40 to 85^oC), and the extended temperature range (-40 to 125^oC). Error due to temperature drift can be calculated by the following equation. Please note that the below equation assumes uses the box method for calculating the error. The box method calculates TC using the difference in the maximum and minimum V_REF measurements over the entire temperature range . For more information about this method, please refer to the article Voltage Reference Selection Basics