Open-circuit detector

1. An open-circuit detector, comprising:

a first current source configured to inject a current at an output of a closed-loop circuit;

a detector configured to monitor a voltage of the closed-loop circuit;

wherein the detector is configured to indicate whether the voltage monitored exceeds a predetermined threshold voltage;

a controller configured to regulate the current injected by the first current source;

wherein the controller is configured to set an open-circuit flag if the current injected caused the voltage to exceed the predetermined threshold voltage; and

wherein the controller is configured to set the open-circuit flag if the voltage exceeded the predetermined threshold voltage within a predetermined time after the current was injected.

2. The detector of claim 1 :

wherein the voltage monitored by the detector is at a regulated output of the closed-loop circuit.

3. The detector of claim 1 :

wherein the voltage monitored by the detector is at a node internal to the closed-loop circuit.

4. The detector of claim 1 :

wherein the controller is configured to cause the first current source to inject the current while the closed-loop circuit is operating.

5. The detector of claim 1 :

wherein the controller is configured to cause the first current source to inject the current at multiple intervals after the closed-loop circuit starts operating and before the closed-loop circuit stops operating.

6. The detector of claim 1 :

wherein the controller is configured to adjust an amplitude or duration of the current injected by the first current source based on a load current drawn at the output of the closed-loop circuit.

7. The detector of claim 1 :

further comprising a current drain coupled between the output and a ground;

wherein the controller is configured to adjust an amount of a current drained by the current drain based on a discharge time of an external load capacitor coupled to the output.

8. The detector of claim 1 :

wherein the output of the closed-loop circuit is configured to be coupled an external capacitor configured to keep the output voltage within a predetermined ripple voltage range; and

wherein the current injected by the current source does not cause the output voltage to exceed the predetermined ripple voltage range.

9. The detector of claim 1 :

wherein the closed-loop circuit is a voltage regulator including an output driver and a compensation capacitor;

wherein the compensation capacitor is coupled to a gate of the output driver;

further comprising a second current source coupled in parallel with the first current source;

wherein the controller is configured to adjust a duration or amplitude of the current injected by the second current source based on a value of the compensation capacitor.

10. The detector of claim 1 :

wherein the closed-loop circuit is a voltage regulator.

11. The detector of claim 10 :

wherein the voltage regulator is a low drop out (LDO) regulator.

12. The detector of claim 10 :

wherein the current is a pull up current injected at an output lead of the voltage regulator.

13. The detector of claim 1 :

wherein the open-circuit detector is embedded within an integrated circuit.

14. The detector of claim 1 :

wherein the detector is coupled to monitor the voltage at an output pin of a chip package.

15. The detector of claim 1 :

wherein the detector is coupled to monitor the voltage at a wire bond between an integrated circuit die and a lead-frame within a chip package.

16. The detector of claim 1 :

wherein the voltage monitored by the detector is at an output of an operational amplifier internal to the closed-loop circuit.

17. An open-circuit detector, comprising:

a first current source configured to inject a current at an output of a closed-loop circuit;

a detector configured to monitor a voltage of the closed-loop circuit;

wherein the detector is configured to indicate whether the voltage monitored exceeds a predetermined threshold voltage;

a controller configured to regulate the current injected by the first current source;

wherein the controller is configured to set an open-circuit flag if the current injected caused the voltage to exceed the predetermined threshold voltage;

further comprising a current drain coupled between the output and a ground;

wherein the controller is configured to adjust an amount of a current drained by the current drain based on a discharge time of an external load capacitor coupled to the output.

18. An open-circuit detector, comprising:

a first current source configured to inject a current at an output of a closed-loop circuit;

a detector configured to monitor a voltage of the closed-loop circuit;

wherein the detector is configured to indicate whether the voltage monitored exceeds a predetermined threshold voltage;

a controller configured to regulate the current injected by the first current source;

wherein the controller is configured to set an open-circuit flag if the current injected caused the voltage to exceed the predetermined threshold voltage;

wherein the output of the closed-loop circuit is configured to be coupled an external capacitor configured to keep the output voltage within a predetermined ripple voltage range; and

wherein the current injected by the current source does not cause the output voltage to exceed the predetermined ripple voltage range.

19. The An open-circuit detector of claim 18 :

wherein the controller is configured to adjust an amplitude or duration of the current injected by the first current source based on a load current drawn at the output of the closed-loop circuit.

20. The An open-circuit detector of claim 18 :

wherein the closed-loop circuit is a voltage regulator including an output driver and a compensation capacitor;

wherein the compensation capacitor is coupled to a gate of the output driver;

further comprising a second current source coupled in parallel with the first current source;

wherein the controller is configured to adjust a duration or amplitude of the current injected by the second current source based on a value of the compensation capacitor.