Circuit and method for a switch matrix and switch sensing
First Claim
1. A switch matrix circuit comprising:
- a plurality of switches organized in a row and column configuration; and
a current sensing circuit coupled to the plurality of switches, the current sensing circuit including a transistor per column of the plurality of switches, and a plurality of resistors each electrically coupled in series with an associated one of the plurality of switches, wherein current amplified by the transistor in a column is sensed as a logic state indicative of a switch status of a switch within the column for a selected row, and wherein the column is configured to conduct at least a threshold current level required for the transistor to perform the amplification if the switch is closed, and to conduct less than the threshold current level if the switch is open, regardless of how many other of the plurality of switches are closed.
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Abstract
Aspects of a switch matrix circuit are provided. In accordance with a circuit aspect, a plurality of switches are organized in a row and column configuration. Coupled to the plurality of switches is a current sensing circuit. The current sensing circuit includes a transistor and at least one resistor per column of the plurality of switches. Current amplified by the transistor and converted by the at least one resistor in a column is sensed as a logic level indicative of a switch status within the column for a selected row. The current sensing arrangement may also be used in an embodiment utilizing bi-directional signal control to minimize the number of I/O lines required to scan the switch matrix. The bi-directional signal scanning may also be implemented in another embodiment that senses voltage levels to determine switch closures.
156 Citations
25 Claims
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1. A switch matrix circuit comprising:
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a plurality of switches organized in a row and column configuration; and a current sensing circuit coupled to the plurality of switches, the current sensing circuit including a transistor per column of the plurality of switches, and a plurality of resistors each electrically coupled in series with an associated one of the plurality of switches, wherein current amplified by the transistor in a column is sensed as a logic state indicative of a switch status of a switch within the column for a selected row, and wherein the column is configured to conduct at least a threshold current level required for the transistor to perform the amplification if the switch is closed, and to conduct less than the threshold current level if the switch is open, regardless of how many other of the plurality of switches are closed. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A circuit for more efficient switch selection sensing, the circuit comprising:
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a switch matrix comprising a plurality of switches organized as a plurality of rows and columns; a current sensing circuit coupled to the switch matrix; and a processor coupled to the switch matrix and the current sensing circuit by a plurality of scan lines, wherein selection of a single row by a scan line returns column current levels from the current sensing circuit to detect if a switch at an intersection of the single row and a column of the switch matrix is closed, and wherein a column current level associated with the column is at least a threshold current level required for detection if the switch is closed, and the column current level associated with the column is less than the threshold current level if the switch is open, regardless of how many other of the plurality of switches are closed. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A method for sensing switch statuses, the method comprising:
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coupling a current sensing circuit to a switch matrix having a plurality of switches in a row and column configuration comprising one switch per row and column intersection; amplifying a current signal; and detecting a switch status of a switch within the switch matrix based on whether a current signal in the current sensing circuit comprises at least a threshold current level, regardless of how many other of the plurality of switches are closed. - View Dependent Claims (14, 15, 16, 17, 18, 19, 24, 25)
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20. A switch matrix circuit comprising:
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a plurality of switches organized in a row and column off-diagonal configuration having one switch per row and column intersection in all but one intersection per row; and a plurality of bi-directional scan lines, wherein a single bi-directional scan line provides both row selection and column sensing capabilities for switch status identification, wherein; a first bi-directional scan line of the plurality of bi-directional scan lines is configured to conduct a first signal associated with a first logic state to a selected row of the switch matrix coupled thereto; a second bi-directional scan line of the plurality of bi-directional scan lines is configured to be scanned for an output signal comprising at least a threshold level, wherein the output signal comprises at least the threshold level only if a scanned switch at an intersection of the selected row and a scanned column of the switch matrix is selected, wherein the scanned column is coupled to the second bi-directional scan line; and each of the other bi-directional scan lines of the plurality of bi-directional scan lines is configured to conduct a second signal associated with a second logic state opposite the first logic state. - View Dependent Claims (21, 22, 23)
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Specification