Pen for use with a touch screen

1. A pen for use with a touch screen, the pen comprises:

a first AC coupling circuit operable to receive a sense signal from the touch screen;

a sense-regulation circuit operable to:

receive the sense signal from the first AC coupling circuit;

compare the sense signal to a reference signal to produce a comparison signal;

generate a regulation signal based on the comparison signal; and

regulate receiving of the sense signal based on the regulation signal;

a response circuit operable to generate a transmit signal based on the comparison signal and data; and

a second AC coupling circuit operable to transmit the transmit signal to the touch screen, wherein the touch screen is capable of interpreting the transmit signal as an input to the touch screen.

2. The pen of claim 1 further comprises:

the first AC coupling circuit including a conductive pen tip; and

the second AC coupling circuit including a conductive pen shell and cone, wherein the conductive pen tip is at least partially physically contained within the cone and is electrically isolated from the conductive pen shell and the cone.

3. The pen of claim 1 further comprises:

the first AC coupling circuit including a conductive pen shell and cone; and

the second AC coupling circuit including a conductive pen tip, wherein the conductive pen tip is at least partially physically contained within the cone and is electrically isolated from the conductive pen shell and the cone.

4. The pen of claim 1 , wherein the sense-regulation circuit comprises:

an operational amplifier having:

a negative input coupled to receive the sense signal;

a positive input coupled to receive the reference signal; and

an output coupled to provide the comparison signal, wherein the comparison signal is representative of an inversion of the sense signal;

a regulation circuit operably coupled to generate the regulation signal based on the comparison signal; and

a dependent supply source operably coupled to provide an adjustment signal to a node coupling the negative input of the operational amplifier to the first AC coupling circuit, wherein the dependent supply source generates the adjustment signal based on the regulation signal.

5. The pen of claim 1 , wherein the sense-regulation circuit comprises:

an operational amplifier having:

a negative input coupled to receive the sense signal;

a positive input coupled to receive the reference signal; and

an output coupled to provide an analog comparison signal, wherein the analog comparison signal is representative of an inversion of the sense signal;

an analog to digital converter operable to convert the analog comparison signal into the comparison signal;

a digital to analog converter operable to convert the comparison signal into the regulation signal; and

a dependent supply source operably coupled to provide an adjustment signal to a node coupling the negative input of the operational amplifier to the first AC coupling circuit, wherein the dependent supply source generates the adjustment signal based on the regulation signal.

6. The pen of claim 1 , wherein the response circuit comprises:

a process module operable to:

receive the comparison signal;

receive the data from a data source of the pen; and

combine the comparison signal and the data to produce an outbound data signal;

a drive circuit operable to convert the outbound data signal into the transmit signal.

7. The pen of claim 6 , wherein the data source comprises:

a pressure sensor coupled to a conductive pen tip, wherein the pressure sensor is operable to:

measure pressure on the conductive pen tip when the conductive pen tip is in physical contact with the touch screen; and

convert the measured pressure into the data.

8. The pen of claim 6 , wherein the data source comprises:

an orientation sensor operable to:

measure three-dimensional orientation of on the pen when the pen is in physical contact with the touch screen; and

convert the measured three-dimensional orientation into the data.

9. The pen of claim 1 , wherein the data comprises:

a null set for basic ring-back touch sensing.

10. A pen for use with a touch screen, the pen comprises:

an AC coupling circuit operable to:

receive a sense signal from the touch screen; and

transmit a transmit signal to the touch screen;

a sense-regulation circuit operable to:

receive the sense signal;

receive a representation of data;

compare the sense signal to the representation of data regarding operation of the pen to produce a comparison signal;

generate a regulation signal based on the comparison signal; and

generate the transmit signal based on the sense signal and the regulation signal; and

a data source circuit operable to generate the data regarding operation of the pen.

11. The pen of claim 10 , wherein the AC coupling circuit comprises one of:

a conductive pen tip; and

a conductive pen shell and cone, wherein the conductive pen tip is at least partially physically contained within the cone and is electrically isolated from the conductive pen shell and the cone.

12. The pen of claim 10 further comprises:

a second AC coupling circuit to transmit a ring-back representation of the sense signal to the touch screen, wherein the touch screen is capable of interpreting the ring-back representation of the sense signal as an input to the touch screen.

13. The pend of claim 10 , wherein the sense-regulation circuit comprises:

an operational amplifier having:

a negative input coupled to receive the sense signal;

a positive input coupled to receive the representation of the data; and

an output coupled to provide the comparison signal;

a regulation circuit operably coupled to generate the regulation signal based on the comparison signal; and

a dependent supply source operably coupled to provide an adjustment signal to a node coupling the negative input of the operational amplifier to the first AC coupling circuit, wherein the dependent supply source generates the adjustment signal based on the regulation signal.

14. The pen of claim 10 , wherein the sense-regulation circuit comprises:

an operational amplifier having:

a negative input coupled to receive the sense signal;

a positive input coupled to receive the representation of the data; and

an output coupled to provide an analog comparison signal;

an analog to digital converter operable to convert the analog comparison signal into the comparison signal;

a digital to analog converter operable to convert the comparison signal into the regulation signal; and

a dependent supply source operably coupled to provide an adjustment signal to a node coupling the negative input of the operational amplifier to the first AC coupling circuit, wherein the dependent supply source generates the adjustment signal based on the regulation signal.

15. The pen of claim 10 further comprises:

the data source circuit including:

a sensing element to:

sense a condition of the pen; and

generate a condition signal based on the sensed condition of the pen;

a data sense circuit operable to generate the data based on the condition signal and a reference signal;

a processing module operable to generate digital outbound data based on the data; and

a digital to analog converter operable to convert the digital outbound data into the representation of the data.

16. The pen of claim 15 , wherein the data sense circuit comprises:

an operational amplifier having:

a negative input coupled to receive the condition signal;

a positive input coupled to receive the reference signal; and

an output coupled to provide the comparison signal, wherein the comparison signal is representative of an inversion of the sense signal;

a regulation circuit operably coupled to generate a second regulation signal based on the comparison signal; and

a dependent supply source operably coupled to provide an adjustment signal to a node coupling the negative input of the operational amplifier to the first AC coupling circuit, wherein the dependent supply source generates the adjustment signal based on the second regulation signal.

17. The pen of claim 10 further comprises:

a receive digital processing module operable to:

receive the comparison signal; and

extract receive data from the comparison signal, wherein the receive data is regarding interoperation of the touch screen and the pen.