Voltage modulator circuit to control light emission for non-invasive timing measurements

• US 20030020448A1
• Filed: 09/24/2002
• Published: 01/30/2003
• Est. Priority Date: 12/29/2000
• Status: Active Grant

• Current Assignee: Harry Muljono, Stefan Rusu
• Original Assignee: Harry Muljono, Stefan Rusu
• Inventors: Rusu, Stefan, Muljono, Harry
• Granted Patent: US 6,995,552 B2
• Time in Patent Office: Days
• US Class Current: 324/76.11
• CPC Class Codes: G01R 29/02 Measuring characteristics of individual pulses, e.g. deviation from pulse flatness, rise time or duration
• CPC Class Codes: G01R 31/311 of integrated circuits G01R31/31728 takes precedence
• CPC Class Codes: G01R 31/31725 Timing aspects, e.g. clock distribution, skew, propagation delay for tester hardware G01R31/31937

Abstract

A non-invasive method and apparatus accurately measures the time difference between two signal edges by optically detecting the emission from a ‘beacon device’ that is modulated as a function of time difference. Through the use of this modulation it is possible to perform timing measurement accurately. Embodiments of a voltage modulator circuit modulate timing information into emission intensity. The method and system of the present invention can be used in applications such as clock skew and pulse width measurements.

Claims

1. A non-invasive method to accurately measure the time difference between two signals comprising detecting the emission from a beacon device the intensity of which is modulated as a function of said time difference.

2. A non-invasive method to accurately measure the time difference between two signals according to claim 1 wherein said time difference is a time difference between two timing signals.

3. A non-invasive method to accurately measure the time difference between two signals according to claim 1 wherein said time difference is a clock skew.

4. A non-invasive method to accurately measure the time difference between two signals according to claim 1 comprising:

a. converting said time difference into a voltage level;

b. supplying said voltage to a beacon device having an emission response; and

c. linearizing the relationship between said emission response and said time difference.

5. A non-invasive method to accurately measure the time difference between two signals according to claim 4 and further comprising detecting the intensity of light emitted from said beacon device.

6. A non-invasive method to accurately measure the time difference between two signals according to claim 5 wherein said step of converting comprises:

a. precharging a capacitor with a supply voltage; and

b. discharging said capacitor for a period equal to the time difference between two signals.

7. A non-invasive method to accurately measure the time difference between two signals according to claim 6 wherein the relationship between said voltage and said time difference in non-linear and said step of linearizing comprises providing a beacon device having a characteristic relationship between voltage and intensity which compensates for said non-linear relationship.

8. A non-invasive method to accurately measure the time difference between two signals according to claim 7 wherein said beacon device is a saturated NMOS transistor.

10. Non-invasive apparatus to accurately measure the time difference between two signals according to claim 5 wherein said time difference is a time difference between two timing signals.

11. Non-invasive apparatus to accurately measure the time difference between two signals according to claim 5 wherein said time difference is a clock skew.

12. Non-invasive apparatus to accurately measure the time difference between two signals according to claim 5 wherein said step voltage modulator circuit comprises:

a. a capacitor from which said modulated output is supplied;

b. a precharge transistor which when actuated couples said capacitor with a supply voltage to precharge it to that voltage; and

c. a discharge circuit coupled to discharge said capacitor for a period equal to said time difference between two signals.

13. Non-invasive apparatus to accurately measure the time difference between two signals according to claim 6 wherein the relationship between said output voltage and said time difference is non-linear and said beacon device has a characteristic relationship between voltage and emission intensity which compensates for said non-linear relationship.

14. Non-invasive apparatus to accurately measure the time difference between two signals according to claim 7 wherein said beacon device comprises a saturated NMOS transistor.

15. Non-invasive apparatus to accurately measure the time difference between two signals according to claim 7 wherein said precharge transistor comprises an NMOS transistor having a source coupled to the supply voltage, a drain coupled to a terminal of said capacitor and a gate, the capacitor having another terminal coupled to ground.

16. Non-invasive apparatus to accurately measure the time difference between two signals according to claim 7 wherein said discharge circuit comprises a series circuit made up two qualifying devices, a PMOS device and an NMOS device, the PMOS device driven by a first of said two signal and the NMOS device driven by a second of said two signals, said PMOS device coupled to one terminal of said capacitor.

17. Non-invasive apparatus to accurately measure the time difference between two signals according to claim 16 wherein said first signal is a “

CLKEarly”

signal and said second signal is a “

CLKLate”

signal.

18. Non-invasive apparatus to accurately measure the time difference between two signals according to claim 16 and further including first and second switching devices respectively between said PMOS device and said NMOS device and said first and second signals.

9. Non-invasive apparatus to accurately measure the time difference between two signals having edges delayed with respect to one another comprising:

a. a voltage modulator circuit receiving the two signals as inputs and providing an output voltage modulated with said timing difference;

b. a beacon device receiving the output voltage of said modulator circuit and converting it into an emission intensity.

19. Apparatus to accurately measure the time difference between two signals comprising:

a. a beacon device having an emission response;

b. means to modulate the intensity of the beacon device as a function of the time difference; and

c. means to detect an emission from the beam device.

20. Apparatus to accurately measure the time difference between two signals according to claim 19 wherein said means to modulate comprise:

a. means to convert said time difference into a voltage level;

b. means to supply said voltage to the beacon device; and

c. means to linearize the relationship between said emission response and said time difference.

21. Apparatus to accurately measure the time difference between two signals according to claim 20 wherein said means to convert comprise:

a. means to precharge a capacitor with a supply voltage; and

b. means to discharging said capacitor for a period equal to the time difference between two signals.

22. Apparatus to accurately measure the time difference between two signals according to claim 20 wherein the relationship between said voltage and said time difference is non-linear and means to linearize comprise a beacon device having a characteristic relationship between voltage and intensity which compensates for said non-linear relationship.

23. Apparatus to accurately measure the time difference between two signals according to claim 22 wherein said beacon device in a saturated NMOS transistor.