Methods and devices for automatic gain control

1. A controller operable to:

check control bits;

sample a first signal at a frequency that is indicated by the checked control bits, the first signal indicating an initial amplitude of an output signal of an oscillator circuit;

select a step amount based on the sampled first signal and a target amplitude of the output signal; and

generate a control signal for the oscillator circuit based on the selected step amount, the control signal indicating a change in gain for the oscillator circuit according to the selected step amount.

2. The controller of claim 1 , operable to select the step amount from among a plurality of step amounts including at least a first step amount and a second step amount, the first step amount being greater than the second step amount.

3. The controller of claim 2 , operable to select the first step amount when a difference between the initial amplitude and the target amplitude is greater than a first threshold.

4. The controller of claim 3 , operable to select the second step amount when the difference is less than the first threshold and greater than a second threshold, wherein the second threshold is smaller than the first threshold.

5. The controller of claim 2 , wherein the first step amount is an integer multiple of the second step amount.

6. The controller of claim 1 , operable to:

adjust levels of the plurality of step amounts based on the checked control bits.

7. A device comprising:

an oscillator circuit operable to generate an output signal;

a first converter operable to convert the output signal into a first signal, the first signal indicating an initial amplitude of the output signal; and

controller operable to,

check control bits,

sample the first signal at a frequency that is indicated by the checked control bits,

select a step amount based on the sampled first signal and a target amplitude of the output signal, and

generate a control signal for the oscillator circuit based on the selected step amount, the control signal indicating a change in gain for the oscillator circuit according to the selected step amount.

8. The device of claim 7 , wherein the oscillator circuit includes a crystal oscillator, wherein the first signal is a digital signal, and wherein the controller is operable to:

determine a difference between a level of the sampled first signal and a target level, the target level being based on the target amplitude; and

determine that an absolute value of the difference is not less than a least significant bit (LSB) of the sampled first signal, and in response, select the step amount as a value equal to a product of the absolute value and a scaling factor, wherein the scaling factor is indicated by the control bits.

9. The device of claim 7 , further comprising:

a second converter operable to convert the control signal into a power supply signal for the driving oscillator circuit; and

a transistor including a source, a gate, and a drain, wherein,

a first terminal of the oscillator circuit is electrically connected to the drain, an input of the first converter and an output of the second converter,

a second terminal of the oscillator circuit is electrically connected to the gate.

10. The device of claim 9 , wherein,

an output of the first converter is electrically connected to a first input of the controller,

an output of the controller is electrically connected to an input of the second converter, and

the first converter is an analog to digital converter and the second converter is digital to analog converter.

11. The device of claim 9 , wherein the controller is operable to select the step amount from among a plurality of step amounts including at least a first step amount and a second step amount, the first step amount being greater than the second step amount.

12. The device of claim 11 , wherein the controller is operable to,

select the first step amount if a difference between the initial amplitude and the target amplitude is greater than a first threshold, and

select the second step amount if the difference is less than the first threshold and greater than a second threshold, wherein the second threshold is smaller than the first threshold.

13. The device of claim 12 , wherein,

the first converter and the second converter have at least 8-bit resolutions such that the first signal and the control signal are at least 8-bit digital signals, and

each of the difference, the first threshold, and the second threshold is represented as an 8-bit value.

14. The device of claim 11 , wherein the first step amount is an integer multiple of the second step amount.

15. The device of claim 7 , wherein the controller is operable to:

adjust levels of the plurality of step amounts based on the checked control bits.

16. A method, comprising:

checking control bits;

sampling a first digital signal at a frequency indicated by the checked control bits, the first digital signal indicating an initial amplitude of an output signal of an oscillator circuit;

selecting a step amount based on the first digital signal and a target amplitude of the output signal; and

generating a second digital signal based on the selected step amount, the second digital signal indicating a change in gain for the oscillator circuit according to the selected step amount.

17. The method of claim 16 , wherein the selecting selects the step amount from among a plurality of step amounts including at least a first step amount and a second step amount, the first step amount being greater than the second step amount.

18. The method of claim 17 , wherein the selecting selects the first step amount when a difference between the initial amplitude and the target amplitude is greater than a first threshold.

19. The method of claim 18 , wherein the selecting selects the second step amount when the difference is less than the first threshold and greater than a second threshold, wherein the second threshold is smaller than the first threshold.

20. The method of claim 17 ,

wherein the checked control bits control levels of the plurality of step amounts.