To measure temperature, a common method utilizes a sensor to convert the quantity to be measured to a voltage. Common solid state sensors utilize semiconductor diode Vbe, the difference in Vbe at two current densities or delta Vbe, or a MOS threshold to provide a temperature dependent output voltage. The temperature is determined from the voltage measurement. Once the sensor output is converted to a voltage it is compared it to a voltage reference. It is common to utilize a voltage reference having a low temperature coefficient such as a bandgap circuit as the voltage reference. The bandgap voltage reference is about 1.2 volts. An n-bit analog to digital converter divides the bandgap reference down by 2n and determines how many of these small pieces are needed to sum up to the converted voltage. The precision of the A/D output is no better than the precision of the bandgap reference.
Typical plots of the output bandgap voltage with respect to temperature are bowed and are therefore of reduced accuracy.
Prior bandgap voltage curvature correction solutions result in very complicated circuits whose performance is questionable.
USPTO Backgrounds
USPTO Backgrounds