Four current transistor temperature sensor and method

• US 6,554,469 B1
• Filed: 04/17/2001
• Issued: 04/29/2003
• Est. Priority Date: 04/17/2001
• Status: Expired due to Term

• Current Assignee: Adeia Semiconductor Advanced Technologies Inc. (f/k/a Tessera Advanced Technologies, Inc.) (Adeia Inc.)
• Original Assignee: Analog Devices, Inc.
• Inventors: Thomson, David, Blake, John, Manus, Lorcan Mac
• Primary Examiner(s): Gutierrez, Diego
• Assistant Examiner(s): VERBITSKY, GAIL KAPLAN
• Application Number:
  US09/837,816
• Time in Patent Office: 742 Days
• Field of Search: 374/163, 374/183, 374/178, 702/64-65, 702/130, 702/FOR-103, 327/512, 327/513
• US Class Current: 374/178
• CPC Class Codes: G01K 7/01 using semiconducting elements having PN junctions G01K7/02, G01K7/16, G01K7/30 take precedence

Abstract

A four current transistor temperature sensor comprises a p-n junction, preferably the base-emitter junction of a bipolar transistor, which is driven with four different currents in a predetermined sequence. Each of the four currents induces a respective base-emitter voltage, which is measured. The temperature of the transistor is calculated based on the values of the four driving currents and the four measured base-emitter voltages. The four driving currents (I1, I2, I3 and I4) are preferably arranged such that I1=2*I3, I2=2*I4, I1/I2=A and I3/I4=A, where A is a predetermined current ratio. I1 and I2 produce respective base-emitter voltages which are subtracted from each other to produce ΔV_be1, and I3 and I4 produce respective base-emitter voltages which are subtracted from each other to produce ΔV_be2. When so arranged, the difference between ΔV_be1 and ΔV_be2 is entirely due to the effect of series base and emitter resistances r_b and r_e. Therefore, the ΔV_be1−ΔV_be2 value provides a correction factor which enables temperature measurement errors due to r_b and r_e to be eliminated.

Claims

1. A transistor temperature sensing system, comprising:

a p-n junction, said p-n junction comprising the base-emitter junction of a bipolar transistor,

at least one current source arranged to provide four different currents to said junction in a predetermined sequence, said junction and said at least one current source arranged such that each of said four currents induces a respective voltage across said junction, and

a voltage measurement means connected to measure each of said induced junction voltages,

wherein said four different currents are I1, I2, I3 and I4, respectively, and wherein I1=n*I3, I2=n*I4, I1/I2=A and I3/I4=A, where A is a predetermined current ratio.

2. The temperature sensing system of claim 1, wherein said voltage measurement means produces voltage measurements V_be1−

V_be2 and V_be3−

V_be4 when currents I1, I2, I3 and I4 are provided to said transistor in sequence, further comprising a processor arranged to calculate the temperature T of said transistor in accordance with;

3. The temperature sensing system of claim 2, wherein said voltage measurement means comprises:

a signal conditioning circuit which receives V_be1 and V_be2 and produces Δ

V_be1, and which receives V_be3 and V_be4 and produces Δ

V_be2, and

an analog-to-digital converter (ADC) having an input which receives Δ

V_be1 and Δ

V_be2 from said signal conditioning circuit, converts Δ

V_be1 and Δ

V_be2 to respective digital values, and provides said digital values to said processor.

4. The temperature sensing system of claim 3, wherein said processor comprises at least two registers and a subtractor, said processor arranged to control said at least one current source to provide said four current values to said transistor, to receive said digital values from said ADC, and to calculate Δ

V_be1−

Δ

V_be2, and

5. A transistor temperature sensing system, comprising:

a p-n junction,

at least one current source arranged to provide four different currents to said junction in a predetermined sequence, said junction and said at least one current source arranged such that each of said four currents induces a respective voltage across said junction, and

a voltage measurement means connected to measure each of said induced junction voltages,

wherein said at least one current source comprises a current mirror having an input transistor and two output transistors, the outputs of said output transistors connected to provide two of said four different currents when said input transistor is driven with a first current and the other two of said four different currents when said input transistor is driven with a second current.

6. A transistor temperature sensing system, comprising:

a bipolar transistor,

at least one current source arranged to provide currents I1, I2, I3 and I4 to said transistor in a predetermined sequence, wherein I1=2*I3, I2=2*I4, I1/I2=A and I3/I4=A, where A is a predetermined current ratio, said transistor and said at least one current source arranged such that each of I1, I2, I3 and I4 induces a respective voltage between said transistor'"'"'s base and emitter,

a voltage measurement means connected to produce voltage measurements V_be1−

V_be2 and V_be3−

V_be4 when currents I1, I2, I3 and I4 are provided to said transistor in sequence, and

a processor arranged to calculate the temperature T of said transistor in accordance with;

7. The temperature sensing system of claim 6, wherein said voltage measurement means comprises:

a signal conditioning circuit which receives V_be1 and V_be2 and produces Δ

V_be1, and which receives V_be3 and V_be4 and produces Δ

V_be2 and

an analog-to-digital converter (ADC) having an input which receives Δ

V_be1 and Δ

V_be2 from said signal conditioning circuit, converts Δ

V_be1 and Δ

V_be2 to respective digital values, and provides said digital values to said processor.

8. The temperature sensing system of claim 7, wherein said processor comprises first and second registers and a subtractor, said processor arranged to control said at least one current source to provide said four current values to said transistor, to receive said digital values from said ADC, and to calculate Δ

V<sub>be1−

Δ

Vbe2</sub>, and Δ

V_be1−

[2*(Δ

V_be1−

Δ

V_be2)] and/or Δ

V_be2−

(Δ

V_be1−

Δ

V_be2).

9. The temperature sensing system of claim 8, wherein said at least one current source comprises a current mirror having an input transistor and two output transistors, the outputs of said output transistors connected to provide two of said four different currents when said input transistor is driven with a first current and the other two of said four different currents when said input transistor is driven with a second current, said processor further arranged to control the current provided to said input transistor.

10. A temperature sensing method, comprising:

forcing currents I1, I2, I3 and I4 through a p-n junction in sequence, wherein II=n*I3, I2=n*I4, I1/I2=A and I3/I4=A, where A is a predetermined current ratio, such that I1, I2, I3 and I4 produce respective voltages V1, V2, V3 and V4 across said junction,

measuring V1, V2, V3 and V4,

determining the temperature T of said junction in;

accordance with;

11. The method of claim 10, wherein said p-n junction comprises a bipolar transistor and said currents I1, I2, I3 and I4 produce respective voltages V1, V2, V3 and V4 across said transistor'"'"'s base-emitter junction.

12. The method of claim 10, wherein n=2 and