Circuit for detecting a voltage change using a time-to-digital converter
A circuit for detecting a voltage change is described. The circuit includes a supply insensitive pulse generator that generates a pulse signal. The circuit also includes a time-to-digital converter coupled to the supply insensitive pulse generator. The time-to-digital converter generates a digital signal based on the pulse signal and a voltage. The circuit also includes a controller coupled to the time-to-digital converter that detects a voltage change based on the digital signal.
1. A circuit for detecting a voltage change, comprising:
a supply insensitive pulse generator that generates a pulse signal;
a time-to-digital converter coupled to the supply insensitive pulse generator, wherein the time-to-digital converter generates a digital signal based on the pulse signal and a voltage; and
a controller coupled to the time-to-digital converter that detects a voltage change based on the digital signal.
2. The circuit of claim 1 , wherein the controller generates a droop code only when the voltage change is a voltage drop.
3. The circuit of claim 2 , wherein the controller resets the droop code if no additional voltage drop occurs within a period.
4. The circuit of claim 1 , wherein the controller is coupled to a phase-locked loop that generates a clock signal for a processor, and wherein the controller adjusts a frequency of the clock signal based on the voltage change.
5. The circuit of claim 4 , wherein the controller adjusts the frequency of the clock signal by switching off an injection signal from a slave voltage-controlled oscillator and adjusting a variable current source.
6. The circuit of claim 1 , wherein the controller generates a calibration code to adjust the pulse signal from the supply insensitive pulse generator.
7. The circuit of claim 6 , wherein the controller generates the calibration code by incrementing the calibration code until the digital signal is within a range.
8. The circuit of claim 1 , wherein the supply insensitive pulse generator generates the pulse signal based on a frequency-divided clock signal.
9. The circuit of claim 1 , wherein the digital signal comprises a thermometer code.
10. The circuit of claim 9 , wherein the controller comprises a decoder that decodes the thermometer code into a 4-bit number.
11. A method for detecting a voltage change by a circuit, comprising:
generating a pulse signal by a supply insensitive pulse generator;
generating a digital signal by a time-to-digital converter based on the pulse signal and a voltage; and
detecting a voltage change based on the digital signal.
12. The method of claim 11 , further comprising generating a droop code only when the voltage change is a voltage drop.
13. The method of claim 12 , further comprising resetting the droop code if no additional voltage drop occurs within a period.
14. The method of claim 11 , further comprising adjusting a frequency of a clock signal for a processor based on the voltage change.
15. The method of claim 14 , wherein adjusting the frequency of the clock signal comprises switching off an injection signal from a slave voltage-controlled oscillator and adjusting a variable current source.
16. The method of claim 11 , further comprising generating a calibration code to adjust the pulse signal from the supply insensitive pulse generator.
17. The method of claim 16 , wherein generating the calibration code comprises incrementing the calibration code until the digital signal is within a range.
18. The method of claim 11 , wherein the pulse signal is generated based on a frequency-divided clock signal.
19. The method of claim 11 , wherein the digital signal comprises a thermometer code.
20. The method of claim 19 , further comprising decoding the thermometer code into a 4-bit number.
21. A computer-program product for detecting a voltage change, comprising a non-transitory tangible computer-readable medium having instructions thereon, the instructions comprising:
code for causing a circuit to generate a pulse signal by a supply insensitive pulse generator;
code for causing the circuit to generate a digital signal by a time-to-digital converter based on the pulse signal and a voltage; and
code for causing the circuit to detect a voltage change based on the digital signal.
22. The computer-program product of claim 21 , the instructions further comprising code for causing the circuit to generate a droop code only when the voltage change is a voltage drop.
23. The computer-program product of claim 22 , the instructions further comprising code for causing the circuit to reset the droop code if no additional voltage drop occurs within a period.
24. The computer-program product of claim 21 , the instructions further comprising code for causing the circuit to adjust a frequency of a clock signal for a processor based on the voltage change.
25. The computer-program product of claim 21 , the instructions further comprising code for causing the circuit to generate a calibration code to adjust the pulse signal from the supply insensitive pulse generator.
26. An apparatus for detecting a voltage change, comprising:
means for generating a pulse signal that is insensitive to variations in supply voltage;
means for generating a digital signal based on the pulse signal and a voltage; and
means for detecting a voltage change based on the digital signal.
27. The apparatus of claim 26 , further comprising means for generating a droop code only when the voltage change is a voltage drop.
28. The apparatus of claim 27 , further comprising means for resetting the droop code if no additional voltage drop occurs within a period.
29. The apparatus of claim 26 , further comprising means for adjusting a frequency of a clock signal for a processor based on the voltage change.
30. The apparatus of claim 26 , further comprising means for generating a calibration code to adjust the pulse signal.