US 7,010,440 B1 · 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

Abstract

A switched current temperature sensing circuit (1) comprises a measuring transistor (Q1) which is located remotely of a measuring circuit (5) which applies three excitation currents (I1,I2,I3) of different values to the measuring transistor (Q1) in a predetermined current sequence along lines (10,11). Resulting base/emitter voltages from the measuring transistor (Q1) are applied to the measuring circuit (5) along the same two lines (10,11) as the excitation currents are applied to the measuring transistor (Q1). Voltage differences ΔVbe 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 (Q1). By virtue of the fact that the measuring transistor (Q1) 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 (Q1) is selected to minimize the voltages in the integrating circuit (36) during integration of the voltage differences ΔVbe.

Claims59

Dependent claims

A method for determining temperature of a device which exhibits an exponential relationship between temperature and a voltage in response to an excitation current, comprising the acts of:

sequentially applying at least three excitation currents of different values to the device along a current path in a predetermined current sequence for sequentially exciting the device for developing successive voltage values across the device in response to the excitation currents;
sensing successive voltages developed across two sensing nodes in the current path on opposite sides of the device in response to the excitation currents;
and
combining the differences of the successive sensed voltages for determining a voltage indicative of the temperature of the device;
wherein,
the predetermined current sequence is selected so that as the differences of the successive sensed voltages developed across the two sensing nodes in the current path are being combined, the cumulative effect, in the sensed voltages, of voltage components resulting from series resistance in the current path between the two sensing nodes through the device is minimised, and
the number of times the device is subjected to excitation by the excitation currents during the predetermined current sequence is selected so that the effect of the voltage components resulting from the series resistance in the current path between the two sensing nodes in the determined voltage indicative of the temperature of the device is substantially eliminated.

4 more elements

A measuring circuit for determining temperature of a device which exhibits an exponential relationship between temperature and voltage in response to an excitation current, the circuit comprising:

a current supply circuit for supplying at least three excitation currents of different values for exciting the device,
a first switch circuit for selectively and sequentially applying the excitation currents to the device along a current path for sequentially exciting the device for developing successive voltage values across the device in response to the excitation currents,
an integrating circuit coupled to two sensing nodes in the current path on opposite sides of the device for sensing successive voltages developed across the sensing nodes in response to the excitation currents, and for combining the differences of the successive sensed voltages for determining a voltage indicative of the temperature of the device,
a control circuit for controlling the first switch circuit for
applying the excitation currents to the device in a predetermined current sequence so that the successive sensed voltages developed across the two sensing nodes in response to the excitation currents in the predetermined current sequence is such that as the differences of the successive sensed voltages are being combined in the integrating circuit, the cumulative effect, in the sensed voltages, of voltage components resulting from series resistance in the current path between the two sensing nodes through the device is minimised, and
controlling the number of times the excitation currents are applied to the device in the predetermined current sequence so that the effect of the voltage components resulting from the series resistance in the current path between the two sensing nodes in the determined voltage indicative of the temperature of the device is substantially eliminated.

3 more elements

Dependencies are inferred from the claim text.

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

Life of this patent

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

Life of this patent

Abstract

Claims59