Method for sensing integrated circuit temperature including adjustable gain and offset

• US 7,808,068 B2
• Filed: 09/11/2008
• Issued: 10/05/2010
• Est. Priority Date: 09/14/2004
• Status: Expired due to Fees

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Agere Systems Incorporated (Broadcom, Inc.)
• Inventors: Hartley, Paul
• Primary Examiner(s): NGO, NGAN V
• Application Number:
  US12/208,671
• Publication Number:
  US 20090002062A1
• Time in Patent Office: 754 Days
• Field of Search: 257/467, 323/233, 323/313, 323/315, 327/512, 327/539, 327/541, 327/543
• US Class Current: 257/467
• CPC Class Codes: G01K 7/01 using semiconducting elements having PN junctions G01K7/02, G01K7/16, G01K7/30 take precedence

Abstract

Embodiments of the invention include a temperature sensor method for providing an output voltage response that is linear to the temperature of the integrated circuit to which the temperature sensor belongs and/or the integrated circuit die on which the temperature sensor resides. The output voltage of the temperature sensor has an adjustable gain component and an adjustable voltage offset component that both are adjustable independently based on circuit parameters. The inventive temperature sensor includes an offset circuit that diverts a portion of current from the scaled PTAT current before the current is sourced through the output resistor. The offset circuit includes a bandgap circuit arrangement, a voltage to current converter arrangement, and a current mirror arrangement that are configured to provide a voltage offset adjustable based on independent circuit parameters such as resistor value ratios and transistor device scaling ratios. The gain of the temperature sensor also is based on similar independent circuit parameters.

Claims

1. A method for sensing the temperature of an integrated circuit, comprising the steps of:

generating a proportional to absolute temperature (PTAT) current I_PTAT that is proportional to absolute temperature (T);

scaling the PTAT current I_PTAT by a factor of N to generate an N-scaled PTAT current;

diverting with an offset circuit an offset portion of current I_OFF from the N-scaled PTAT current, the offset circuit having a bandgap voltage V_BG across an offset resistor R_OFF;

sourcing the remaining, non-diverted portion of the N-scaled PTAT current through a temperature sensor resistor R_TS as a temperature sensor current I_TS;

generating an output voltage V_TS by the flow of the temperature sensor current I_TS through the temperature sensor resistor R_TS, the output voltage V_TS being a function of the absolute temperature T and a function of the bandgap voltage V_BG; and

offsetting the voltage across the temperature sensor resistor R_TS by a voltage offset V_OFF, wherein the voltage offset V_OFF is the bandgap voltage V_BG multiplied by a scaling factor P and multiplied by the ratio of the temperature sensor resistor R_TS to an offset resistor R_OFF.

2. The method as recited in claim 1, wherein the voltage offset V_OFF is adjustable based on the ratio of the temperature sensor resistor R_TS to the offset resistor R_OFF.

3. The method as recited in claim 1, wherein the PTAT current I_PTAT generating step generates the PTAT current I_PTAT using a current source that includes a current source resistor R_PTAT, and wherein the output voltage V_TS has a gain that is adjustable based on the ratio of the temperature sensor resistor R_TS to the current source resistor R_PTAT.

4. The method as recited in claim 1, wherein the diverting step includes the steps of:

generating a bandgap current I_BG based on the bandgap voltage V_BG and the offset resistor R_OFF, and

scaling the bandgap current I_BG by a factor of P to generate a P-scaled bandgap current, wherein the P-scaled bandgap current determines the offset current I_OFF that is diverted from the N-scaled PTAT current.

5. The method as recited in claim 4, wherein the step of generating the bandgap current I_BG generates the bandgap current I_BG using a voltage to current converter, and wherein the voltage to current converter comprises:

an op-amp having an inverting input, a non-inverting input, and an output,

a first field effect transistor (FET) having a gate coupled to the output of the op-amp, a source coupled to an upper supply voltage V_DD, and a drain coupled to the inverting input of the op-amp,

a second FET having a gate coupled to the output of the op-amp and the gate of the first FET, a source coupled to the upper supply voltage V_DD, and a drain coupled to the second current mirror, and

a resistor coupled between the lower supply voltage V_SS and the drain of the first FET and the inverting input of the op-amp,

wherein the voltage potential at the non-inverting input of the op-amp is the bandgap voltage V_BG.

6. The method as recited in claim 1, wherein the generating step generates the PTAT current I_PTAT using a first current source that includes a current source resistor R_PTAT, and wherein the offset circuit includes:

a bandgap circuit for generating the bandgap voltage V_BG,

a voltage to current converter, coupled to the bandgap circuit, for generating a bandgap current I_BG based on the bandgap voltage V_BG and the offset resistor R_OFF, and

a second current mirror coupled between the voltage to current converter, the first current mirror and the temperature sensor resistor R_TS, the second current mirror having the scaling factor P for scaling the bandgap current I_BG to determine the voltage V_OFF.

7. The method as recited in claim 1, wherein the bandgap voltage V_BG is based on the voltage potential of the integrated circuit.

8. A method for detecting the temperature of one or more integrated circuits chips on an integrated circuit die, the method comprising the steps of:

generating with a current source a PTAT current I_PTAT that is proportional to absolute temperature T, the current source including a resistor R_PTAT;

scaling with a current mirror having a scaling factor of N the PTAT current I_PTAT to generate an N-scaled PTAT current;

diverting with an offset circuit an offset portion of current I_OFF from the N-scaled PTAT current generated by the current mirror, the offset circuit having a bandgap voltage V_BG across an offset resistor R_OFF;

sourcing the remaining, non-diverted portion of the N-scaled PTAT current through a temperature sensor resistor R_TS as a temperature sensor current I_OUT,

generating an output voltage V_TS by the flow of the temperature sensor current I_TS through the temperature sensor resistor R_TS, the output voltage V_TS being a function of the absolute temperature T and a function of the bandgap voltage V_BG,

wherein the temperature sensor has a gain that is based on the ratio of the temperature sensor resistor R_TS to the current source resistor R_PTAT, and

wherein the temperature sensor has a voltage offset that is based on the ratio of the temperature sensor resistor R_TS to the offset resistor R_OFF.

9. The method as recited in claim 8, wherein the current mirror further comprises a first current mirror, wherein the offset circuit further comprises a bandgap circuit and a second current mirror, and wherein the diverting step further comprises the steps of:

generating, with a bandgap circuit and a voltage to current converter, a bandgap current I_BG based on the bandgap voltage V_BG and the offset resistor R_OFF, and

scaling with a second current mirror having a scaling factor of P the bandgap current I_BG by a factor of P, wherein the P-scaled bandgap current determines the offset current I_OFF that is diverted from the N-scaled PTAT current.

10. The method as recited in claim 9, wherein the current mirror includes a unit transistor device and a P-scaled transistor device, and wherein the scaling factor P is based on the size of the P-scaled transistor device.

11. The method as recited in claim 8, wherein the bandgap voltage V_BG is based on the voltage potential of the integrated circuit.

12. The method as recited in claim 8, wherein the offset circuit further comprises:

a first circuit portion that generates a bandgap current I_BG based on the bandgap voltage V_BG and the offset resistor R_OFF, and

a second circuit portion, coupled to the first circuit portion, that scales up the bandgap current I_BG to determine the offset current I_OFF diverted from the N-scaled PTAT current.

13. The method as recited in claim 8, wherein the voltage to current converter further comprises:

an op-amp having an inverting input, a non-inverting input, and an output,

a first field effect transistor (FET) having a gate coupled to the output of the op-amp, a source coupled to the upper supply voltage V_DD, and a drain coupled to the inverting input of the op-amp,

a second FET having a gate coupled to the output of the op-amp and the gate of the first FET, a source coupled to the upper supply voltage V_DD, and a drain coupled to the second current mirror, and

a resistor coupled between the lower supply voltage V_SS and the drain of the first FET and the inverting input of the op-amp,

wherein the voltage potential at the non-inverting input of the op-amp is the bandgap voltage V_BG.