Programmable impedance output driver

A method for matching a desired impedance with an output impedance of an output driver circuit comprising the steps of:

• a) programming said desired impedance into said output driver circuit;
• b) comparing a voltage of said desired impedance with an evaluate voltage and generating a signal indicating which of said voltages is higher;
• c) generating a first and second count from said signal, wherein said second count corresponds to a prior first count;
• d) modifying said evaluate voltage with said first count to more closely resemble said voltage of said desired impedance;
• e) selecting and outputting the lowest of said first and second count;
• and
• f) generating an output impedance corresponding to said output of said lowest of said first and second count.

A system having an output driver circuit, said system comprising:

• an external resistance device for programming a desired impedance into said output driver circuit;
• a voltage comparative device, coupled to said external resistance device, for comparing a voltage of said desired impedance with an evaluate voltage and generating a signal indicating which of said voltages is higher;
• a control logic device, coupled to said voltage comparative device, for receiving said signal and generating a first and second count from said signal, wherein said second count corresponds to a prior first count;
• an evaluate device, coupled to said control logic device and said voltage comparative device, for receiving said first count and modifying said evaluate voltage with said first count to more closely resemble said voltage of said desired impedance;
• a low select device, coupled to said control logic device, for receiving said first and second count, and selecting and outputting the lowest of said first and second count;
• and
• an output device, coupled to said low select device, for receiving said output of said low select device and generating an output impedance corresponding to said output of said low select device.