Process corner estimation circuit with temperature compensation

• US 7,634,746 B1
• Filed: 08/23/2006
• Issued: 12/15/2009
• Est. Priority Date: 11/14/2005
• Status: Active Grant

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Chan, Wai Cheong
• Primary Examiner(s): WHITMORE, STACY
• Application Number:
  US11/508,684
• Time in Patent Office: 1,210 Days
• Field of Search: 716/2, 716/4, 716/6, 327/100, 327/113, 327/175, 327/540, 327/543, 327/513, 323/274
• US Class Current: 716/136
• CPC Class Codes: G06F 2119/12 Timing analysis or timing optimisation
• CPC Class Codes: G06F 30/367 Design verification, e.g. using simulation, simulation program with integrated circuit emphasis [SPICE], direct methods or relaxation methods

Abstract

A process corner estimation circuit with temperature compensation is included in each die formed from a silicon wafer in order to quickly and easily provide a determination of process corner. The temperature compensation circuitry provides input current to a clock generator, the input current to the clock generator being inversely proportional to the temperature of the die. The clock generator circuit of the indicator circuit includes an array of flip-flop elements and is run at a lower operating voltage, such that the differences in delay in the generated timing signal are accentuated for different process corners. The period of the timing signal is determined using slow and fast clock counters, with the slow clock counting a number of cycles of the timing signal and the fast clock counting a number of cycles of a fixed frequency. The count produced by the fast clock corresponds to the delay in the clock generator circuit, giving a temperature compensated indication of the process corner of the die.

Claims

1. A temperature compensated process corner estimation circuit for determining an appropriate process corner from a distribution of possible process corners for a die including the process corner estimation circuit, the process corner estimation circuit comprising:

a clock generator circuit operable in response to an input current to generate a timing signal, the frequency of the timing signal depending upon the determined process corner of the die;

a logic module operable to receive the timing signal from the clock generator circuit and output a signal in response thereto that corresponds to the determined process corner of the die; and

a regulator circuit that provides the input current to the clock generator circuit, the input current being inversely proportional to the temperature of the die, the regulator circuit including

(i) an operational amplifier that receives a reference voltage at its positive input;

(ii) an MOS transistor having its gate connected to receive the output of the operational amplifier;

(iii) a resistor having a positive temperature coefficient connected between the MOS transistor and a negative supply voltage, whereby the voltage across the resistor is fixed and the current flowing through the resistor is inversely proportional to the temperature of the die; and

(iv) a current mirror that mirrors the current flowing through the resistor to the clock generator as the input current to the clock generator.

2. A process corner estimation circuit as in claim 1, and wherein:

the clock generator circuit is operated at a lower supply voltage than the operating supply voltage of the die, thereby reducing the frequency of the timing signal.

3. A process corner estimation circuit as in claim 2, and further comprising:

a level shifting circuit operable to level shift the timing signal from the lower supply voltage to the operating supply voltage.

4. A process corner estimation circuit as claim 1, and wherein:

the clock generator circuit includes a plurality of flip-flop elements configured to increase differences in the frequency of the timing signal across the distribution of process corners.

5. A process corner estimation circuit as in claim 1, and wherein:

the logic module includes a slow clock counter operable to receive the timing signal from the clock generator circuit, the slow clock counter operable to count a predetermined number of cycles of the timing signal and output a hold signal in response thereto.

6. A process corner estimation circuit as in claim 5, and wherein:

the logic module further includes a fast clock counter operable to receive a fast frequency signal having a predetermined frequency, the fast clock counter operable to count a number of cycles of the fast frequency signal until the hold signal is received from the slow clock counter, and output a period count signal in response thereto.

7. A process corner estimation circuit as in claim 6, and further comprising:

a trigger voltage source operable to switch a trigger voltage from a first voltage level to a second voltage level in order to start the indicator circuit.

8. A method for determining the process corner of a die using a process corner indicator circuit contained on the die, comprising the steps of:

generating a periodic timing signal using a clock generator circuit in the process corner indicator circuit;

providing temperature compensation to the clock generator circuit;

determining the period of the periodic timing signal;

using the period to determine the process corner of the die; and

selecting a lower supply voltage for the clock generator circuit than the normal operating supply voltage for the die, whereby the period of the timing signal is increased.

9. A method as in claim 8, and further comprising:

level shifting the timing signal from the lower supply voltage to the operating supply voltage.

10. A method as in claim 8, and further comprising:

providing a plurality of flip-flop elements configured to increase differences in the period of the timing signal between various process corners.

11. A method as in claim 8, and further comprising:

sending a trigger signal to the process corner indicator circuit in order to activate the process corner indicator circuit.

12. A method as in claim 8, and wherein:

determining the period of the periodic timing signal includes receiving the timing signal to a slow clock counter operable to count a predetermined number of cycles of the timing signal and output a hold signal in response thereto.

13. A method as in claim 12, and wherein:

determining the period of the periodic timing signal further includes receiving a fast frequency signal having a predetermined frequency to a fast clock counter operable, the fast clock counter operable to count a number of cycles of the fast frequency signal until the hold signal is received from the slow clock counter, and output a period count signal in response thereto.

14. A temperature compensated process corner estimation circuit for determining an appropriate process corner from a distribution of possible process corners for a die that includes the process corner estimation circuit, comprising:

a clock generator circuit that responds to an input signal to generate a timing signal, the frequency of the timing signal depending upon the process corner of the die, the clock generator circuit being operated at a lower supply voltage than the operating supply voltage of the die and including a plurality of flip-flop elements, thereby increasing differences in the frequency of the timing signal between process corners across the process corner distribution;

a temperature compensation circuit that generates the input signal, the input signal being inversely proportional to the temperature of the die;

a slow clock counter operable to receive the timing signal from the clock generator circuit, the slow clock counter operable to count a predetermined number of cycles of the timing signal and output a hold signal in response thereto; and

a fast clock counter operable to receive a fast frequency signal having a predetermined frequency, the fast clock counter operable to count a number of cycles of the fast frequency signal until the hold signal is received from the slow clock counter, and output a period count signal in response thereto.