IMAGING SYSTEMS WITH VERIFICATION CIRCUITRY FOR MONITORING STANDBY LEAKAGE CURRENT LEVELS

• US 20130027566A1
• Filed: 02/17/2012
• Published: 01/31/2013
• Est. Priority Date: 07/25/2011
• Status: Active Grant

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Inventors: Solhusvik, Johannes, Skaug, Steffen
• Granted Patent: US 8,860,817 B2
• Time in Patent Office: Days
• US Class Current: 348/187
• CPC Class Codes: H04N 1/00021 Picture signal circuits
• CPC Class Codes: H04N 1/00031 Testing, i.e. determining the result of a trial H04N1/00029 takes precedence; using test signals for transmission mode changing H04N2201/33371
• CPC Class Codes: H04N 1/00034 Measuring, i.e. determining a quantity by comparison with a standard H04N1/00031 takes precedence
• CPC Class Codes: H04N 1/00053 out of service, i.e. outside of normal operation
• CPC Class Codes: H04N 1/00063 using at least a part of the apparatus itself, e.g. self-testing
• CPC Class Codes: H04N 1/00074 Indicating or reporting details of user-machine interface H04N1/0035
• CPC Class Codes: H04N 1/195 the array comprising a two-dimensional array or a combination of two-dimensional arrays
• CPC Class Codes: H04N 23/65 Control of camera operation in relation to power supply

Abstract

Imaging systems may be provided with image sensors having verification circuitry. Verification circuitry may be configured to continuously or occasionally verify that the image sensor is functioning properly. For example, verification circuitry may be configured to monitor levels of leakage current during standby mode. Verification circuitry may be coupled between a power supply and circuitry that is powered by that power supply. When the imaging system is in standby mode, circuitry associated with the imaging system such as pixel circuitry may draw a standby leakage current. Verification circuitry may be configured to measure the amount of standby leakage current drawn by associated imaging system circuitry. If the measured level of standby leakage current exceeds a maximum acceptable level of standby leakage current, a warning signal may be generated. Standby leakage current levels on multiple power supply lines may be monitored with associated verification circuitry.

Claims

1. An image sensor having an image capture mode and a standby mode comprising:

a power supply;

image sensor circuitry operable to receive at least one supply voltage signal from the power supply;

verification circuitry coupled between the power supply and the image sensor circuitry, wherein the verification circuitry is operable to measure a level of leakage current drawn by the image sensor circuitry when the image sensor is in the standby mode.

2. The image sensor defined in claim 1 wherein the verification circuitry comprises:

a power supply switch coupled between the power supply and the image sensor circuitry, wherein the power supply switch is operable to be turned on during image the capture mode and is operable to be turned off during the standby mode.

3. The image sensor defined in claim 2 wherein the verification circuitry further comprises:

a resistor in parallel with the power supply switch, wherein the resistor has first and second terminals.

4. The image sensor defined in claim 3 wherein the verification circuitry further comprises:

a differential amplifier having first and second input terminals coupled respectively to first and second terminals of the resistor.

5. The image sensor defined in claim 4 wherein the differential amplifier has an output terminal and is operable to generate at its output terminal a leakage voltage that is proportional to the level of standby leakage current drawn by the image sensor circuitry when the image sensor is in the standby mode.

6. The image sensor defined in claim 5 wherein the verification circuitry further comprises:

a comparator having first and second input terminals, wherein the first input terminal is coupled to the output terminal of the differential amplifier and is operable to receive the leakage voltage, wherein the second input terminal is operable to receive a threshold voltage, and wherein the comparator is operable to determine if the leakage voltage exceeds the threshold voltage.

7. The image sensor defined in claim 1 wherein the image sensor circuitry comprises an image pixel and wherein the image pixel is operable to receive a supply voltage signal from the power supply.

8. A method, comprising:

at a first time, operating an imaging system in an image capture mode;

at a second time, operating the imaging system in a standby mode, wherein the imaging system comprises a power supply, image sensor circuitry, and verification circuitry coupled between the power supply and the image sensor circuitry; and

with the verification circuitry, measuring a level of leakage current drawn by the image sensor circuitry during the standby mode.

9. The method defined in claim 8 wherein the verification circuitry comprises a power supply switch coupled between the power supply and the image sensor circuitry, the method further comprising:

with the verification circuitry, determining that the imaging system is in the standby mode; and

with the verification circuitry, turning the power supply switch off.

10. The method defined in claim 9 wherein the verification circuitry further comprises a resistor in parallel with the power supply switch and wherein measuring the level of leakage current drawn by the image sensor circuitry during the standby mode comprises measuring the level of leakage current passing through the resistor during the standby mode.

11. The method defined in claim 10 wherein the verification circuitry further comprises a differential amplifier and wherein measuring the level of leakage current passing through the resistor comprises:

with the differential amplifier, measuring a voltage drop across the resistor.

12. The method defined in claim 10 wherein the verification circuitry further comprises a comparator, the method further comprising:

with the comparator, comparing the measured level of leakage current passing through the resistor during the standby mode with a maximum acceptable level of leakage current.

13. The method defined in claim 12 further comprising:

with the verification circuitry, determining that the measured level of leakage current exceeds the maximum acceptable level of leakage current; and

with the verification circuitry, generating a warning signal and conveying the warning signal to external circuitry.

14. A method, comprising:

at a first time, operating an integrated circuit in an active mode;

at a second time, operating the imaging system in a standby mode, wherein the integrated circuit comprises a power supply, circuitry, and verification circuitry coupled between the power supply and the circuitry; and

with the verification circuitry, measuring a level of leakage current drawn by the circuitry during the standby mode to determine whether or not the circuitry is damaged.

15. The method defined in claim 14 wherein determining whether or not the circuitry is damaged comprises determining whether or not the level of leakage current drawn by the circuitry during the standby mode exceeds a maximum acceptable level of leakage current.

16. The method defined in claim 15 wherein the verification circuitry comprises a power supply switch coupled between the power supply and the circuitry, the method further comprising:

with the verification circuitry, determining that the integrated circuit is in the standby mode; and

with the verification circuitry, turning the power supply switch off.

17. The method defined in claim 16 wherein the verification circuitry further comprises a resistor in parallel with the power supply switch and wherein measuring the level of leakage current drawn by the circuitry during the standby mode comprises measuring the level of leakage current passing through the resistor during the standby mode.

18. The method defined in claim 17 wherein the verification circuitry further comprises a differential amplifier and wherein measuring the level of leakage current passing through the resistor comprises:

with the differential amplifier, measuring a voltage drop across the resistor.

19. The method defined in claim 18 wherein the verification circuitry further comprises a comparator, the method further comprising:

with the comparator, comparing the measured level of leakage current passing through the resistor with a maximum acceptable level of leakage current.

20. The method defined in claim 19 further comprising:

with the verification circuitry, determining that the measured level of leakage current exceeds the maximum acceptable level of leakage current; and

with the verification circuitry, generating a warning signal and conveying the warning signal to external circuitry.