Patent ID: 7068065

Claim:
A system for controlling impedance on a data line comprising: an output driver circuit for providing an impedance adjustable to a target impedance and responsive to control signals from a control sense circuit; a control sense circuit, responsive to a reference current for sensing the impedance of the output driver circuit and for providing a control current on an output lead in response to the reference current and to signals from a digital controller, such that the control current is set to a plurality of values between a minimum value and a maximum value by the signals from the step adjustment controller; a replica circuit comprising a replica branch equal to a portion of 2 b (exponent b where b is an integer) parallel resistances of the output driver for converting the control current of the control sense circuit into a control voltage a voltage comparator means for comparing the control voltage to a reference voltage and for producing a feedback signal to the digital controller, such that when the control voltage is equal to the reference voltage the digital controller produces a control signal to the control sense circuit that locks the line driver circuit to the target impedance.