System for compensating for temperature induced delay variation in an integrated circuit

• US 6,005,408 A
• Filed: 07/31/1997
• Issued: 12/21/1999
• Est. Priority Date: 07/31/1997
• Status: Expired due to Fees

• Current Assignee: Credence Systems Corporation (COHU Incorporated)
• Original Assignee: Credence Systems Corporation (COHU Incorporated)
• Inventors: Gillette, Garry C.
• Primary Examiner(s): Ballato, Josie
• Assistant Examiner(s): KOBERT, RUSSELL MARC
• Application Number:
  US08/904,081
• Time in Patent Office: 873 Days
• Field of Search: 327/262, 327/512, 327/513, 324/765, 324/158.1, 324/760
• US Class Current: 324/762.02
• CPC Class Codes: H03K 19/00323 Delay compensation
• CPC Class Codes: H03K 19/00384 in field effect transistor circuits

Abstract

A delay compensation circuit responds to a sensed change in operating temperature of a CMOS integrated circuit (IC) by appropriately adjusting the IC'"'"'s power supply voltage so as to prevent the temperature change from affecting IC signal path delays. The delay compensation circuit senses the temperature change by monitoring a temperature sensitive voltage across a diode included in the IC and generates the power supply voltage as an appropriately adjusted linear function of the diode voltage.

Claims

1. A method for controlling a signal path delay in an integrated circuit wherein the signal path delay is influenced by a temperature of the integrated circuit and by a voltage of a power supply signal input to the integrated circuit, the method comprising the steps of:

sensing a threshold voltage of a diode incorporated into said integrated circuit, wherein said threshold voltage is indicative of said temperature of said integrated circuit and

controlling said power supply signal voltage such that said power supply signal voltage is a function of the sensed threshold voltage.

2. The method in accordance with claim 1 wherein the step of controlling said power supply signal voltage comprises adjusting said sower supply signal voltage in response to changes in the sensed threshold voltage such that said signal path delay does not change substantially with said temperature of said integrated circuit.

3. The method in accordance with claim 1 wherein the step of controlling said power supply signal voltage comprises the steps of:

increasing said power supply signal voltage when the sensed threshold voltage increases, and

decreasing the power supply signal voltage when the sensed threshold voltage decreases.

4. An apparatus for controlling a signal path delay in an integrated circuit wherein the signal path delay is influenced by a temperature of the integrated circuit and by a voltage of a power supply signal input to the integrated circuit, the apparatus comprising:

a diode incorporated into said integrated circuit, said diode having a threshold voltage that varies with the temperature of said integrated circuit, and

controller means for sensing said threshold voltage and for adjusting the power supply signal voltage such that the power supply signal voltage is a function of said threshold voltage.

5. The apparatus in accordance with claim 4 wherein said controller means adjusts said power supply signal voltage in response to changes in said threshold voltage such that said signal path delay remains substantially invariant with respect to the temperature of said integrated circuit.

6. The apparatus in accordance with claim 5 wherein said controller means comprises means for supplying a current through said diode such that said threshold voltage develops across said diode.

7. The apparatus in accordance with claim 6 wherein said controller means further comprises:

means for amplifying said threshold voltage across said diode to produce a control voltage, and

means receiving said control voltage for producing said power supply signal, wherein said power supply signal voltage is a function of said control voltage.

8. The apparatus in accordance with claim 4 wherein said power supply signal voltage is a linear function of said temperature of said integrated circuit.

9. An apparatus for transmitting a test signal to a circuit device under test, the apparatus comprising:

means for generating a timing signal;

an integrated circuit receiving a power supply signal and including a signal path for receiving said timing signal and for generating said test signal in response to said timing signal following a signal path delay that is a function of a temperature of said integrated circuit and of a voltage of said power supply signal;

a diode incorporated into said integrated circuit, said diode having a threshold voltage that varies with the temperature of said integrated circuit, and

controller means for sensing said threshold voltage and for adjusting said power supply signal voltage such that the power supply signal voltage is a function of said threshold voltage.

10. The apparatus in accordance with claim 9 wherein said controller means comprises:

means for supplying a current through said diode such that said threshold voltage develops across said diode.

11. The apparatus in accordance with claim 10 further comprises:

means for amplifying said threshold voltage across said diode to produce a control voltage; and

means receiving said control voltage for producing said power supply signal, wherein a voltage of said power supply signal is a function of said control voltage.

12. The apparatus in accordance with claim 11 wherein said voltage of said power supply signal is a linear function of said temperature of said integrated circuit.