Transmit/receive switch for a touch-screen system
View Patent ↗An apparatus that is configurable to perform a forward scan, a row scan, and a column scan is disclosed. The apparatus includes a path selection module coupled to a transmitter and a receiver. The path selection module includes a row-transmit switch, a column-receive switch, a row-receive switch, and a column-transmit switch that are configurable to form various transmit paths and receive paths to perform the forward scan, a row scan, and a column scan. The row-transmit switch and the column-transmit switch cascades switching transistors to protect against large voltage swings present in an output of the transmitter, controls the gate voltage that is applied to these switching transistors to protect against the large voltage swings, and includes additional protection circuitry to ensure their reliability. The column-receive switch and the row-receive switch uses thick oxide transistors to protect thin oxide transistors against the large voltage swings and/or includes additional protection circuitry to ensure their reliability.
1. A touch-screen system, comprising:
a touch-screen including a plurality of rows and a plurality of columns that are arranged to form a touch sensitive area; and
a transceiver coupled to the touch-screen, the transceiver including:
a transmitter,
a receiver, and
a switching module configured to:
couple the transmitter to a corresponding row from among the plurality of rows and to couple a corresponding column from among the plurality of columns to the receiver in a pass-through mode of operation, and
couple the transmitter to the corresponding column and to couple the corresponding row to the receiver in a crossover mode of operation.
2. The touch-screen system of claim 1 , wherein the switching module comprises:
a butterfly switching circuit including a plurality of switches that are configurable to form:
a row-transmit path configured to couple the transmitter to the corresponding row in the pass-through mode of operation,
a column-receive path configured to couple the corresponding column to the receiver in the pass-through mode of operation,
a column-transmit path configured to couple the transmitter to the corresponding column in the crossover mode of operation, and
a column-receive path configured to couple the corresponding row to the receiver in the crossover mode of operation.
3. The touch-screen system of claim 2 , wherein the plurality of switches comprises:
a row-transmit switch;
a column-receive switch;
a row-receive switch; and
a column-transmit switch,
wherein the row-transmit switch is closed and the column-transmit switch is open to form the row-transmit path,
wherein the column-receive switch is closed and the row-receive switch is open to form the column-receive path,
wherein the row-transmit switch is open and the column-transmit switch is closed to form the column-transmit path, and
wherein the column-receive switch is open and the row-receive switch is closed to form the column-receive path.
4. The touch-screen system of claim 3 , wherein the row-transmit switch or the column-transmit switch comprise:
a first p-type transistor;
a second p-type transistor coupled to the first p-type transistor;
a first n-type transistor; and
a second n-type transistor coupled to the first n-type transistor.
5. The touch-screen system of claim 4 , further comprising:
a switch protection circuit configured to pass a fixed switch protection reference between a drain of the first p-type transistor and a source of the second p-type transistor when the first and the second p-type transistors are non-conducting.
6. The touch-screen system of claim 4 , wherein the first and the second p-type transistors are configured to be activated by applying a p-type turn-on gate voltage to their respective gates, and wherein the first and the second n-type transistors are configured to be activated by applying an n-type turn-on gate voltage to their respective gates.
7. The touch-screen system of claim 6 , further comprising:
a gate control module configured to provide the p-type turn-on gate voltage and the n-type turn-on gate voltage based upon an output of the transmitter.
8. The touch-screen system of claim 7 , wherein the p-type turn-on gate voltage or the n-type turn-on gate voltage is characterized as having a substantially similar frequency and phase as the output of the transmitter.
9. The touch-screen system of claim 7 , wherein the gate control module comprises:
a bias control module configured to provide a first bias current and a second bias current;
a p-type turn-on voltage control module configured to operate upon the output of the transmitter to reduce a voltage swing of the output of the transmitter and to translate a mean of the output of the transmitter to provide the p-type turn-on gate voltage in response to the first bias current; and
an n-type turn-on voltage control module configured to operate upon the output of the transmitter to reduce a voltage swing of the output of the transmitter and to translate a mean of the output of the transmitter to provide the n-type turn-on gate voltage in response to the second bias current.
10. The touch-screen system of claim 6 , wherein the first p-type transistor is configured to be deactivated by applying the n-type turn-on gate voltage to its respective gate, and
wherein the first n-type transistor is configured to be deactivated by applying the p-type turn-on gate voltage to its respective gate.
11. The touch-screen system of claim 10 , further comprising:
a switch bank including:
an activation switch configured to apply the p-type turn-on gate voltage to the first p-type transistor,
a deactivation switch configured to apply the n-type turn-on gate voltage to the first p-type transistor,
an activation switch protection circuit configured to apply a first fixed switch protection reference to the activation switch when the deactivation switch applies the n-type turn-on gate voltage to the first p-type transistor, and
a deactivation switch protection circuit configured to apply a second fixed switch protection reference to the deactivation switch when the activation switch applies the p-type turn-on gate voltage.
12. The touch-screen system of claim 1 , wherein the touch-screen system is implemented as part of a mobile device.
13. A switching module, comprising:
a row-transmit switch configured to couple a transmitter to a first port of the switching module in a pass-through mode of operation;
a column-receive switch configured to couple a second port of the switching module to a receiver in the pass-through mode of operation;
a row-receive switch configured to couple the transmitter to the second port in a crossover mode of operation;
a column-transmit switch configured to couple the first port to the receiver in the crossover mode of operation;
a gate control module configured to provide a p-type turn-on gate voltage and an n-type turn-on gate voltage based upon an output of the transmitter, the p-type turn-on gate voltage and the n-type turn-on gate voltage being applied to activate the row-transmit switch in the pass-through mode of operation or the column-transmit switch in the crossover mode of operation.
14. The switching module of claim 13 , wherein the p-type turn-on gate voltage or the n-type turn-on gate voltage is characterized as having a substantially similar frequency and phase as the output of the transmitter.
15. The switching module of claim 13 , wherein the gate control module comprises:
a bias control module configured to provide a first bias current and a second bias current;
a p-type turn-on voltage control module configured to determine a voltage swing and a mean value of the p-type turn-on gate voltage in response to the first bias current; and
an n-type turn-on voltage control module configured to determine a voltage swing and a mean value of the n-type turn-on gate voltage in response to the second bias current.
16. The switching module of claim 13 , wherein the row-transmit switch or the column-transmit switch comprise:
a first p-type transistor;
a second p-type transistor coupled to the first p-type transistor;
a first n-type transistor; and
a second n-type transistor coupled to the first n-type transistor.
17. The switching module of claim 16 , wherein the first and the second p-type transistors are configured to be activated by applying the p-type turn-on gate voltage to their respective gates, and wherein the first and the second n-type transistors are configured to be activated by applying the n-type turn-on gate voltage to their respective gates.
18. The switching module of claim 17 , wherein the first p-type transistor is configured to be deactivated by applying the n-type turn-on gate voltage to its respective gate, and wherein the first n-type transistor is configured to be deactivated by applying the p-type turn-on gate voltage to its respective gate.
19. The switching module of claim 13 , wherein the column-receive switch or the row-receive switch comprise:
a first n-type thin-oxide switching transistor;
a second n-type thin-oxide switching transistor coupled to the first n-type thin-oxide switching transistor;
a first n-type native thick-oxide switching transistor coupled to the second n-type thin-oxide switching transistor; and
a second n-type native thick-oxide switching transistor coupled to the first n-type native thick-oxide switching transistor.
20. The switching module of claim 19 , wherein the first n-type thin-oxide switching transistor, the second n-type thin-oxide switching transistor, and the first n-type native thick-oxide switching transistor are configured to be activated in response to a first reference voltage, and wherein the second n-type native thick-oxide switching transistor is configured to be activated in response to a second reference voltage.