Patent ID: 7791367
Filing Date: 2010-09-07
Classification: H03K

Abstract:
1. A driver circuit in an integrated circuit having selectable output impedance, comprising: a variable value resistor coupled between a node and a reference voltage terminal; a calibrator circuit having an input coupled to a first integrated circuit pad and an output coupled to the node, the calibrator circuit establishing a predetermined constant voltage at the node; and a controlled impedance circuit having an input for receiving data from circuitry within the integrated circuit and an output for providing the data to a second integrated circuit pad of the integrated circuit, the controlled impedance circuit conducting a calibration current determined by the variable value resistor for controlling an output impedance of the driver circuit at the second integrated circuit pad, the controlled impedance circuit varying resistance of the variable value resistor in a calibration mode to select the calibration current which determines a predetermined output impedance at the second integrated circuit pad.