Leakage efficient anti-glitch filter with variable delay stages

1. An anti-glitch filter circuit comprising:

a plurality of variable delay stages; and

a coincidence detector element for detecting coincidence of an input signal to said plurality of variable delay stages and an output signal of said plurality of variable delay stages; and

a glitch-filtered output signal output from said coincidence detector element.

2. The anti-glitch filter circuit of claim 1 wherein in said glitch-filtered output signal, spurious signals characterized as having a duration of less than a delay of said plurality of variable delay stages are substantially eliminated.

3. The anti-glitch filter circuit of claim 2 wherein said coincidence detector comprises a Mueller-C element.

4. The anti-glitch filter circuit of claim 2 wherein said plurality of variable delay stages comprises a plurality of inverters.

5. The anti-glitch filter circuit of claim 4 wherein said plurality of inverters comprises a stacked inverter circuit.

6. The anti-glitch filter circuit of claim 5 wherein said stacked inverter circuit comprises at least two p-type devices coupled in series with at least two n-type devices.

7. The anti-glitch filter circuit of claim 6 wherein said stacked inverter circuit is characterized in having a greater switching time duration than an inversion performed by an inverter comprising only two active devices.

8. The anti-glitch filter circuit of claim 6 wherein said stacked inverter circuit is characterized in having less leakage current than an inverter comprising only two active devices.

9. The anti-glitch filter circuit of claim 6 wherein said stacked inverter circuit comprises:

a first plurality of devices of a first type coupled in series;

a second plurality of devices of a second type coupled in series, wherein said second type is opposite to said first type; and

wherein said first and said second pluralities of devices are coupled in series and comprise at least five active devices.

10. The anti-glitch filter circuit of claim 2 wherein said plurality of variable delay stages comprises a plurality of NAND gates.

11. The anti-glitch filter circuit of claim 10 wherein said plurality of NAND gates comprises a stacked NAND gate.

12. The anti-glitch filter circuit of claim 11 wherein said stacked NAND gate comprises two p-type devices coupled in series with four n-type devices.

13. The anti-glitch filter circuit of claim 12 wherein said stacked NAND gate is characterized in having a greater switching time duration than a switching time duration of a NAND gate comprising only four active devices.

14. The anti-glitch filter circuit of claim 12 wherein said stacked NAND gate is characterized in having less leakage current than a NAND gate comprising only four active devices.

15. The anti-glitch filter circuit of claim 12 wherein said stacked NAND gate comprises:

a first plurality of devices of a first type coupled in series;

a second plurality of devices of second type coupled in series, wherein said second type is opposite to said first type;

a third plurality of devices of said second type coupled in series;

a fourth plurality of devices of said first type coupled in series;

wherein said first second and third pluralities of devices are coupled in series;

wherein gates of said first and third pluralities of devices are coupled to a first input signal;

wherein gates of said second and fourth pluralities of devices are coupled to a second input signal; and

wherein non-power terminals of said first and fourth pluralities of devices are coupled to form an output signal of said stacked NAND gate.

16. A method of delaying an electronic signal comprising:

accessing an electronic signal;

producing a delayed version of said electronic signal through a variable number of delay stages; and

combining said electronic signal and said delayed version of said electronic signal to produce a substantially glitch-free delayed electronic signal, wherein said glitch-free delayed electronic signal transitions in response to a coincidence of said electronic signal and said delayed version of said electronic signal.

17. The method of claim 16 wherein said combining comprises filtering glitches characterized as having a duration of less than a delay of said delayed version of said electronic signal.

18. The method of claim 16 wherein said combining is performed using a Mueller-C element.

19. The method of claim 16 wherein said producing is performed using a plurality of inverters.

20. The method of claim 19 wherein said plurality of inverters comprise a stacked inverter circuit.

21. The method of claim 20 wherein said stacked inverter circuit comprises at least two p-type devices coupled in series with at least two n-type devices.

22. The method of claim 21 wherein said stacked inverter circuit is characterized in having a greater switching time duration than an inversion performed by an inverter comprising only two active devices.

23. The method of claim 21 wherein said stacked inverter circuit is characterized in having less leakage current than an inverter comprising only two active devices.

24. The method of claim 21 wherein said stacked inverter circuit comprises:

a first plurality of devices of a first type coupled in series;

a second plurality of devices of a second type coupled in series, wherein said second type is opposite to said first type; and

wherein said first and said second pluralities of devices are coupled in series and comprise at least five active devices.

25. An electronic circuit comprising:

a plurality of delay stages comprising a plurality of stacked inverters coupled in series, each of said plurality of stacked inverters comprising:

at least two devices of a first type coupled in series, coupled in series to

at least two devices of a second type coupled in series, wherein said second type is opposite to said first type;

a plurality of multiplexers corresponding to said plurality of delay stages for selecting between a signal present at a desired delay stage and a signal propagating from beyond a delay stage corresponding to a multiplexer;

a coincidence detector circuit comprising:

first and second devices of a first type coupled in series, coupled in series to

third and fourth devices of a second type coupled in series; and

wherein an input to said plurality of delay stages is coupled to gates of said first and fourth devices and an output of said plurality of delay stages is coupled to gates of said second and third devices.

26. The electronic circuit of claim 25 wherein gates of each device comprising each of said plurality of stacked inverters are coupled together.

27. The electronic circuit of claim 25 wherein each of said plurality of stacked inverters are substantially identical.

28. The electronic circuit of claim 25 wherein each of said plurality of stacked inverters comprises two p-type devices.

29. The electronic circuit of claim 25 wherein each of said plurality of stacked inverters comprises three n-type devices.

30. The electronic circuit of claim 25 further comprising an inverter coupled to said input of said plurality of delay stages.