ApplicationNo. 06/184952 filed on 09/08/1980
US Classes:341/26, With particular key scanning feature713/321Programmable calculator with power saving feature
ExaminersPrimary: Brigance, Gerald L.
Attorney, Agent or Firm
International ClassesH03K 17/94 (20060101)
H03K 17/96 (20060101)
H03M 11/00 (20060101)
H03M 11/20 (20060101)
AbstractA keyboard system includes a row and a column matrix of electrically isolated conductors with a key switch at each intersection which is effective, when closed, to electrically connect the associated intersecting row and column conductors. The conduction path of a column transistor is connected between each column conductor and a first power terminal and the gate-to-source region of a respective row transistor is connected between each row conductor and a second power terminal. The column transistors are turned-on prior to any switch closure. Therefore, when a switch is closed, its associated column transistor provides a very low impedance, low voltage drop, path between the first power terminal and the row transistor connected to the row conductor associated with the switch. The row transistor is then turned-on if the operating voltage applied between the first and second power terminal exceeds the threshold voltage of the row transistor. A normally off pulse generating system is coupled between the drains of the row transistors and the control electrodes of the column transistors. The pulse operating system is activated in response to a switch closure and sequentially scans the column transistors. The column transistor whose column conductor is connected to a closed switch then produces a signal indicative of the closure. The circuitry in the pulse generating system is operable down to one threshold voltage, whereby the whole system operates at very low voltages.