Ring oscillator circuit and method of regulating aggregate charge stored within capacitive loading therefor
A ring oscillator circuit comprising a plurality of stages operably coupled output-to-input in a ring configuration. A frequency tuning stage comprises an inverting logic gate and a delay component. The delay component comprises a first capacitive component comprising a first terminal operably coupled to an output of the inverting logic gate and a second terminal operably coupled to a first reference voltage at least when the ring oscillator is disabled. The delay component further comprises a further capacitive component comprising a first terminal operably coupled to the output of the inverting logic gate and a second terminal selectively couplable to the first reference voltage and a second reference voltage. The second terminal of the further capacitive component is arranged to be operably coupled to the first reference voltage when the ring oscillator is enabled, and operably coupled to the second reference voltage when the ring oscillator is disabled.
1. A ring oscillator circuit comprising a plurality of stages operably coupled output-to-input in a ring configuration; at least one of the stages of the ring oscillator circuit comprises a frequency tuning stage, the at least one frequency tuning stage comprising an inverting logic gate and a delay component; the delay component comprising:
a first capacitive component comprising a first terminal operably coupled to an output of the inverting logic gate and a second terminal operably coupled to a first reference voltage at least when the ring oscillator is disabled, the first reference voltage comprising one of a high reference voltage and a low reference voltage; and
at least one further capacitive component comprising a first terminal operably coupled to the output of the inverting logic gate and a second terminal selectively couplable to the first reference voltage and a second reference voltage, the second reference voltage comprising the other of the high reference voltage and the low reference voltage;
wherein the second terminal of the at least one further capacitive component is arranged to be operably coupled to the first reference voltage when the ring oscillator is enabled, and operably coupled to the second reference voltage when the ring oscillator is disabled.
2. The ring oscillator circuit of claim 1 , wherein the delay component is arranged such that, upon the ring oscillator circuit being enabled and the second terminal of the at least one further capacitive component being operably coupled to the first reference voltage at time t=t0, a redistribution of charge within the capacitive components of the delay component at time t=t0+Δt achieves a voltage level at the output of the inverting logic gate equal to V_tr+/−ΔV, where V_tr is a transition voltage for the succeeding stage within the ring oscillator circuit and ΔV is an oscillator voltage swing for the ring oscillator circuit.
3. The ring oscillator circuit of claim 1 , wherein the delay component comprises a switching element controllable to selectively couple the second terminal of the at least one further capacitive component to the first reference voltage and the second reference voltage.
4. The ring oscillator circuit of claim 3 , wherein the switching element is controlled by an enable signal for the ring oscillator circuit such that:
when the enable signal is set to disable the ring oscillator circuit, the switching element is controlled to couple the second terminal of the further capacitive component to the second reference voltage; and
when the enable signal is set to enable the ring oscillator circuit, the switching element is configured to couple the second terminal of the further capacitive component to the first reference voltage.
5. The ring oscillator circuit of claim 1 , wherein the second terminal of the at least one further capacitive component is operably coupled to an output of a further logic gate.
6. The ring oscillator circuit of claim 5 , wherein an input of the further logic gate is operably coupled to an enable signal for the ring oscillator circuit.
7. The ring oscillator circuit of claim 5 , wherein the further logic gate comprises one of an inverter and a buffer.
8. The ring oscillator circuit of claim 1 , wherein the second terminal of the first capacitive component is operably coupled to the first reference voltage when the ring oscillator is disabled and when the ring oscillator is enabled.
9. The ring oscillator circuit of claim 1 , wherein the delay component further comprises a flying capacitance comprising a first terminal operably coupled to the output of the inverting logic gate and a second terminal operably coupled to an input of the inverting logic gate.
10. The ring oscillator circuit of claim 1 , wherein the first capacitive component comprises a flying capacitance, and the second terminal of the first capacitive component is operably coupled to an input of the first capacitive component.
11. The ring oscillator circuit of claim 10 , wherein the delay component further comprises a still further capacitive component comprising a first terminal operably coupled to the output of the inverting logic gate and a second terminal operably coupled to one of the first reference voltage and the second reference voltage when the ring oscillator is disabled and when the ring oscillator is enabled.
12. The ring oscillator circuit of claim 1 , wherein the first and second reference voltages comprise supply voltages.
13. The ring oscillator circuit of claim 1 , wherein the first reference voltage comprises a ground plane.
14. The ring oscillator circuit of claim 1 , wherein the second reference voltage comprises a positive supply voltage.
15. The ring oscillator circuit of claim 1 , wherein the inverting logic gate comprises one of an inverter and an exclusive OR gate.
16. The ring oscillator circuit of claim 1 , implemented within an integrated circuit device comprising at least one die within a single integrated circuit package.
17. A method of regulating an aggregate charge stored within a capacitive loading of a delay component for a frequency tuning stage of a ring oscillator circuit, the delay component comprising:
a first capacitive component comprising a first terminal operably coupled to an output of an inverting logic gate of the frequency tuning stage and a second terminal operably coupled to a first reference voltage at least when the ring oscillator is disabled, the first reference voltage comprising one of a high reference voltage and a low reference voltage; and
at least one further capacitive component comprising a first terminal operably coupled to the output of the inverting logic gate and a second terminal selectively couplable to the first reference voltage and a second reference voltage, the second reference voltage comprising the other of the high reference voltage and the low reference voltage;
wherein the method comprises:
operably coupling the second terminal of the at least one further capacitive component to the second reference voltage when the ring oscillator is disabled; and
operably coupling the second terminal of the at least one further capacitive component to the first reference voltage upon the ring oscillator being enabled.