Methods and apparatus for anti-eclipse circuit verification

1. An image sensor, comprising:

a pixel array comprising a plurality pixels arranged in rows and columns;

an anti-eclipse circuit connected to a column of pixels and comprising:

a first transistor responsive to a first eclipse signal; and

a first eclipse enable transistor;

a verification circuit connected to the anti-eclipse circuit and configured to:

control a voltage level of the first eclipse signal; and

detect a failure in the anti-eclipse circuit comprising:

generate a first test output signal;

generate a second test output signal;

generate a difference signal based on the first test output signal and the second output signal; and

determine if the difference signal varies beyond a predetermined range.

2. The image sensor according to claim 1 , wherein the anti-eclipse circuit further comprises a second transistor responsive to a second eclipse signal.

3. The image sensor according to claim 2 , wherein the first transistor is directly connected to the first eclipse enable transistor and the second transistor is directly connected to a second eclipse enable transistor.

4. The image sensor according to claim 2 , wherein the first transistor and the second transistor are connected in parallel with each other and directly connected to the first eclipse enable transistor.

5. The image sensor according to claim 1 , wherein the verification circuit is selectively connected to the anti-eclipse circuit via a switch.

6. The image sensor according to claim 1 , wherein the verification circuit is further connected to the pixel array and controls a row select signal for each row of the pixel array.

7. The image sensor according to claim 1 , wherein the verification circuit:

applies a first voltage level to the first transistor;

reads out a first test output voltage according to the applied first voltage level;

applies a second voltage level to the first transistor;

reads out a second test output voltage according to the applied second voltage level;

computes a difference output voltage by subtracting the first test output voltage from the second test output voltage; and

generates an error signal if the difference output voltage exceeds a predetermined range.

8. A method for detecting circuit failures in an anti-eclipse circuit, comprising:

providing an image sensor comprising the anti-eclipse circuit, wherein the image sensor is configured to:

evaluate circuit connectivity of at least one circuit path from a plurality of circuit paths in the anti-eclipse circuit comprising:

applying a first test signal to the anti-eclipse circuit at a first time;

reading out a first test output signal at a second time;

applying a second test signal to the anti-eclipse circuit at a third time;

reading out a second test output signal at a fourth time;

determining a difference signal between the first and second test output signals after the fourth time; and

determining if the difference signal is within a predetermined voltage range; and

generate an output signal according to the circuit connectivity evaluation.

9. The method according to claim 8 , wherein determining the difference voltage comprises subtracting the first test output signal from the second test output signal.

10. The method according to claim 8 , wherein the plurality of circuit paths comprises:

an eclipse enable line; and

an eclipse DAC line.

11. The method according to claim 10 , wherein the output signal is one of:

an error signal if a circuit failure exists on the circuit path; and

a verification signal if the circuit path is free of a circuit failure.

12. The method according to claim 8 , wherein the image sensor is further configured to select the circuit path from the plurality of circuit paths that is free of a circuit failure.

13. An imaging system, comprising:

a pixel array;

an anti-eclipse circuit connected to the pixel array,

wherein the anti-eclipse circuit comprises:

a first transistor responsive to a first test input signal; a first eclipse enable transistor responsive to an eclipse enable signal; and a second transistor responsive to a second test input signal; and

a verification circuit connected to the anti-eclipse circuit and configured to evaluate circuit connectivity of a circuit path used to control the anti-eclipse circuit, wherein evaluating circuit connectivity comprises:

applying a first voltage to the first transistor at a first time;

reading out a first test output voltage at a second time; applying a second voltage to the first transistor at a third time;

reading out a second test output voltage at a fourth time; and

determining a difference voltage between the first and second test output voltages.

14. The imaging system according to claim 13 , wherein the circuit path comprises at least one of:

an eclipse enable line; and

an eclipse DAC line.