Oscillator circuit

1. An apparatus, comprising:

an oscillator circuit having one or more capacitors and configured and arranged to generate an oscillating signal via repeated charging and discharging of the one or more capacitors; and

a control circuit connected to the oscillator circuit and configured and arranged to set an oscillation frequency of the oscillator circuit as a non-linear function of an input control signal;

wherein the control circuit is configured and arranged to set the oscillation frequency of the oscillator circuit to a frequency scaled by a value raised by an exponent value specified by the input control signal.

2. The apparatus of claim 1 , wherein the oscillator circuit includes

a first capacitor included in the one or more capacitors;

a second capacitor included in the one or more capacitors;

a switching circuit configured to

operate in a first mode in response to the oscillating signal having a first value and operate in a second mode in response to the oscillating signal having a second value;

in the first mode, charge the first capacitor via a resistive path and discharge the second capacitor; and

in the second mode, charge the second capacitor via the resistive path and discharge the first capacitor; and

a comparison circuit configured and arranged to set the oscillating signal to the first value based on a comparison of a voltage of the first capacitor to a first threshold voltage and set the oscillating signal to the second value based on a comparison of a voltage of the second capacitor to a second threshold voltage.

3. The apparatus of claim 2 , wherein the comparison circuit includes

an inverter circuit configured to set the oscillating signal to the first value in response to voltage at a terminal of the first capacitor falling below a threshold voltage; and

a buffer circuit configured to set the oscillating signal to the second value in response to voltage at a terminal of the second capacitor exceeding the threshold voltage.

4. The apparatus of claim 2 , wherein

the oscillator circuit further includes a latch circuit; and

the comparison circuit is configured and arranged to set the oscillating signal to the first value by providing a set control signal to the latch circuit and set the oscillating signal to the second value by providing a reset control signal to the latch circuit.

5. The apparatus of claim 2 , wherein the switching circuit is configured and arranged to

charge the first capacitor by providing a current in a first direction through the resistive path from a first power supply node to the first capacitor; and

charge the second capacitor by providing a current in a second direction through the resistive path from the second capacitor to a second power supply node.

6. The apparatus of claim 1 , wherein the control circuit is configured and arranged to adjust the oscillation frequency by adjusting a resistance of a resistive path of the oscillator circuit used for charging the one or more capacitors and adjusting a capacitance of the one or more capacitors.

7. The apparatus of claim 6 , wherein

the input control signal specifies a numerical value; and

the control circuit includes

a first circuit configured and arranged to determine a target frequency as a function having the numerical value as an exponent; and

a second circuit configured and arranged to

in a first clock cycle, determine a capacitance value and resistance value for the target frequency; and

in a second clock cycle following the first clock cycle, set the oscillation frequency of the oscillator circuit to the target frequency by setting the resistance of the current path to the determined resistance value and setting the capacitance of the one or more capacitors to the determined capacitance value.

8. The apparatus of claim 7 , wherein the second circuit includes a look up table storing respective pairs of resistance and capacitance values for each of a plurality of target frequencies.

9. The apparatus of claim 7 , wherein the second circuit is configured and arranged to determine the target frequency by multiplying a first constant value by a second constant value raise to the power of the numerical value specified by the input control signal.

10. A method comprising:

using an oscillator circuit having one or more capacitors, generating an oscillating signal by repeated charging and discharging of the one or more capacitors; and

adjusting an oscillation frequency of the oscillating signal as a non-linear function of an input control signal;

wherein the adjusting of the oscillation frequency includes setting the oscillation frequency to a frequency scaled by a value raised by an exponent value specified by the input control signal.

11. The method of claim 10 , wherein

the oscillator circuit includes a first capacitor and a second capacitor; and

the generating of the oscillating signal includes

in response to an oscillating signal having a first value, charging the first capacitor via a resistive path and discharge the second capacitor;

in response to an oscillating signal having a second value, charging the second capacitor via the resistive path and discharge the first capacitor;

setting the oscillating signal to the first value based on a comparison of a voltage of the first capacitor to a first threshold voltage; and

setting the oscillating signal to the second value based on a comparison of a voltage of the second capacitor to a second threshold voltage.

12. The method of claim 11 , wherein

the oscillator circuit further includes a latch circuit configured to output the oscillating signal;

the setting the oscillating signal to the first value includes providing a set signal to the latch circuit;

the setting the oscillating signal to the second value includes providing a reset signal to the latch circuit.

13. The method of claim 12 , wherein

the set signal is provided to the latch circuit by an inverter circuit configured to output the first value in response to an input of the inverter having a voltage less than the threshold voltage and output the second value in response to the input of the inverter having a voltage greater than the threshold voltage; and

the set signal is provided to the latch circuit by a buffer circuit configured to output the first value in response to an input of the buffer having a voltage greater than the threshold voltage and output the second value in response to the input of the buffer having a voltage less than the threshold voltage.

14. The method of claim 11 , wherein

the charging of the first capacitor includes providing a current in a first direction through the resistive path from a first power supply node to the first capacitor; and

the charging of the second capacitor includes providing a current in a second direction through the resistive path from the second capacitor to a second power supply node.

15. The method of claim 10 , wherein the adjusting of the oscillation frequency includes adjusting a resistance of a current path of the oscillator circuit connecting a current source to the one or more capacitors and adjusting a capacitance of the one or more capacitors.

16. The method of claim 10 , wherein

the input control signal specifies a numerical value; and

the adjusting of the oscillation frequency includes

in a first clock cycle,

determining a target frequency as a function having the numerical value as an exponent, and

determining a capacitance value and a resistance value for the target frequency; and

in a second clock cycle following the first clock cycle, setting the oscillation frequency of the oscillator circuit to the target frequency by setting a resistance of a current path of the oscillator circuit to the determined resistance value and setting the capacitance of the one or more capacitors to the determined capacitance value.

17. The method of claim 16 , wherein the determining of the capacitance value and the resistance value includes retrieving the capacitance value and resistance value from a look up table storing a respective pair of resistance and capacitance values for each of a plurality of target frequencies.

18. The method of claim 16 , wherein the determining of the target frequency includes multiplying a first constant value by a second constant value raise to the power of the numerical value specified by the input control signal.

19. An apparatus, comprising:

an oscillator circuit having one or more capacitors and configured and arranged to generate an oscillating signal via repeated charging and discharging of the one or more capacitors; and

a control circuit connected to the oscillator circuit and configured and arranged to set an oscillation frequency of the oscillator circuit as a non-linear function of an input control signal;

wherein the control circuit is configured and arranged to adjust the oscillation frequency by adjusting a resistance of a resistive path of the oscillator circuit used for charging the one or more capacitors and adjusting a capacitance of the one or more capacitors; and

wherein the input control signal specifies a numerical value, and the control circuit includes,

a first circuit configured and arranged to determine a target frequency as a function having the numerical value as an exponent; and

a second circuit configured and arranged to

in a first clock cycle, determine a capacitance value and resistance value for the target frequency; and

in a second clock cycle following the first clock cycle, set the oscillation frequency of the oscillator circuit to the target frequency by setting the resistance of the current path to the determined resistance value and setting the capacitance of the one or more capacitors to the determined capacitance value.