Method and a measuring circuit for determining temperature from a PN junction temperature sensor, and a temperature sensing circuit comprising the measuring circuit and a PN junction

摘要

A switched current temperature sensing circuit ( 1 ) comprises a measuring transistor (Q 1 ) which is located remotely of a measuring circuit ( 5 ) which applies three excitation currents (I₁,I₂,I₃) of different values to the measuring transistor (Q 1 ) in a predetermined current sequence along lines ( 10,11 ). Resulting base/emitter voltages from the measuring transistor (Q 1 ) are applied to the measuring circuit ( 5 ) along the same two lines ( 10,11 ) as the excitation currents are applied to the measuring transistor (Q 1 ). Voltage differences DeltaV_be of successive base/emitter voltages resulting from the excitation currents are integrated in an integrating circuit ( 36 ) of the measuring circuit ( 5 ) to provide an output voltage indicative of the temperature of the measuring transistor (Q 1 ). By virtue of the fact that the measuring transistor (Q 1 ) is excited by excitation currents of three different values, the effect of current path series resistance in the lines ( 10,11 ) on the output voltage indicative of temperature is eliminated. The predetermined current sequence in which the excitation currents are applied to the measuring transistor (Q 1 ) is selected to minimize the voltages in the integrating circuit ( 36 ) during integration of the voltage differences DeltaV_be.