Analog to digital conversion circuit with very narrow bandpass digital filtering
An analog to digital conversion circuit includes an analog to digital converter (ADC) circuit operable to convert an analog signal having an oscillation frequency into a first digital signal having a first data rate frequency, where the analog signal includes a set of pure tone components. The analog to digital conversion circuit further includes a digital decimation filtering circuit operable to convert the first digital signal into a second digital signal having a second data rate frequency. The analog to digital conversion circuit further includes a digital bandpass filter (BPF) circuit operable to convert the second digital signal into an outbound digital signal having a third data rate frequency, where the digital bandpass filter circuit is set to produce a bandpass region approximately centered at the oscillation frequency of the analog signal and having a bandwidth tuned for filtering a pure tone.
1. A touch screen sensor array comprises:
a plurality of drive sense circuits; and
a plurality of electrodes operably coupled to the plurality of drive sense circuits, wherein:
a first electrode of the plurality of electrodes has a first self-capacitance,
a second electrode of the plurality of electrodes has a second self-capacitance,
a mutual capacitance exists between the first and second electrodes,
a first drive sense circuit of the plurality of drive sense circuits driving a first signal having
a first frequency component to the first electrode for sensing the first self-capacitance based on the first frequency component of the first signal;
a second drive sense circuit of the plurality of drive sense circuits driving a second signal having the first frequency component and a second frequency component on the second electrode and for sensing the second self-capacitance based on the first frequency component of the second signal; and
the first drive sense circuit sensing the mutual capacitance based on the second frequency component of the second signal.
2. The touch screen sensor array of claim 1 further comprises:
the first drive sense circuit generating a first vector to represent a first sensed first self-capacitance without a touch, wherein the first vector includes a first real component and a first imaginary component; and
the first drive sense circuit generating a second vector to represent a second sensed first self-capacitance with a touch, wherein the second vector includes a second real component and a second imaginary component, wherein the second vector is greater than the first vector.
3. The touch screen sensor array of claim 2 , wherein the touch comprises one of:
a finger touch; and
a pen touch.
4. The touch screen sensor array of claim 1 further comprises:
the first drive sense circuit generating a first vector to represent a first sensed first mutual-capacitance without a touch, wherein the first vector includes a first real component and a first imaginary component; and
the first drive sense circuit generating a second vector to represent a second sensed first mutual-capacitance with a touch, wherein the second vector includes a second real component and a second imaginary component, wherein the second vector is less than the first vector.
5. The touch screen sensor array of claim 1 , wherein the first drive sense circuit comprises:
an analog time domain circuit operably coupled to the first electrode, wherein the analog time domain circuit is operable to:
drive the first signal on the first electrode based on a reference signal; and
sense an effect of the first signal on the first electrode to produce an analog frequency domain error correction signal;
an analog to digital circuit operable to convert the analog frequency domain error correction signal into a digital domain error correction signal; and
a digital frequency domain circuit operable to convert the digital domain error correction signal into digital data that is presentative of the first self-capacitance of the first electrode.
6. The touch screen sensor array of claim 5 , wherein the first drive sense circuit further comprises:
a digital to analog feedback circuit operable to generate an analog feedback representation of the digital domain error correction signal, wherein the analog time domain circuit further produces the analog frequency domain error correction signal based on the analog feedback representation of the digital domain error correction signal.
7. The touch screen sensor array of claim 5 , wherein the digital frequency domain circuit comprises:
a digital decimation filtering circuit operably coupled to decimate the digital domain error correction signal to produce a decimated digital signal; and
a digital bandpass filter operably coupled to bandpass filter the decimated digital signal to produce the digital data.
8. A drive sense circuit comprises:
a connection to a first electrode that has a self-capacitance, wherein a mutual capacitance exists between the first electrode and second electrode; and
circuitry operably coupled to:
drive a first signal having a first frequency component on to the first electrode;
sense the first self-capacitance based on the first frequency component of the first signal; and
sense the mutual capacitance based on a second frequency component of a second signal that was driven on to the second electrode.
9. The drive sense circuit of claim 8 , wherein the drive sense circuit is further operable to:
generate a first vector to represent a first sensed self-capacitance without a touch, wherein the first vector includes a first real component and a first imaginary component; and
generate a second vector to represent a second sensed self-capacitance with a touch, wherein the second vector includes a second real component and a second imaginary component, wherein the second vector is greater than magnitude of the first vector.
10. The drive sense circuit of claim 9 , wherein the touch comprises one of:
a finger touch; and
a pen touch.
11. The drive sense circuit of claim 8 , wherein the drive sense circuit is further operable to:
generate a first vector to represent a first sensed mutual-capacitance without a touch, wherein the first vector includes a first real component and a first imaginary component; and
generate a second vector to represent a second sensed mutual-capacitance with a touch, wherein the second vector includes a second real component and a second imaginary component, wherein the second vector is less than the first vector.
12. The drive sense circuit of claim 8 , wherein the circuitry comprises:
an analog time domain circuit operably coupled via the connection to the first electrode, wherein the analog time domain circuit is operable to:
drive the first signal on the first electrode based on a reference signal; and
sense an effect of the first signal on the first electrode to produce an analog frequency domain error correction signal;
an analog to digital circuit operable to convert the analog frequency domain error correction signal into a digital domain error correction signal; and
a digital frequency domain circuit operable to convert the digital domain error correction signal into digital data that is presentative of the first self-capacitance of the first electrode.
13. The drive sense circuit of claim 12 , wherein the circuitry comprises:
a digital to analog feedback circuit operable to generate an analog feedback representation of the digital domain error correction signal, wherein the analog time domain circuit further produces the analog frequency domain error correction signal based on the analog feedback representation of the digital domain error correction signal.
14. The drive sense circuit of claim 12 , wherein the digital frequency domain circuit comprises:
a digital decimation filtering circuit operably coupled to decimate the digital domain error correction signal to produce a decimated digital signal; and
a digital bandpass filter operably coupled to bandpass filter the decimated digital signal to produce the digital data.