Patent ID: 6759892
Filing Date: 2004-07-06
Classification: G05F,G06G

Abstract:
A temperature compensation method for providing temperature compensated output in a logarithmic voltage output device having a first, second, and third resistor, comprising the steps of:measuring the resistance of said first, second, and third resistor at a first temperature, wherein said first and third resistors comprise thin film resistors and wherein said second resistor comprises a metal resistor; measuring the resistance of said first, second, and third resistor at a second temperature; calculating the PPM of said metal and said thin film resistors from said resistance measurements of said first, Second, and third resistor at said first and second temperatures; and trimming said third resistor according to a temperature compensation trim calculation process, wherein the temperature compensation trim calculation process comprises the step of: calculating a first term wherein said first term is calculated by multiplying the PPM for said metal resistor by the difference between said first and second temperatures and adding one to the result to obtain a numerator, and dividing said numerator by a denominator similarly calculated for the thin film resistor; subtracting a second term from the first term to obtain a third term, wherein said second term is calculated by dividing the electronic charge by the Boltzmann constant, the first temperature, and a logarithmic constant CL and then subtracting one from this result to obtain a second numerator, and dividing said second numerator by a second denominator similarly calculated for said second temperature; and multiplying the third term by both a fourth term and the resistance of said second resistor, as measured at said first temperature, to calculate the trim of said third resistor, wherein said fourth term is calculated by subtracting one from said second term and inverting the result.