Patent ID: 7167020
Filing Date: 2007-01-23
Classification: H03K

Abstract:
1. Apparatus for tuning a digitally controlled input/output (I/O) driver of an integrated circuit for parameter variation compensation, said I/O driver including a first switching network coupled between a bus and a fixed voltage potential, the impedance of said first switching network being controlled by a first digital code, said apparatus comprising: a second switching network coupled between a desired impedance and said fixed voltage potential, the impedance of said second switching network being controlled by a second digital code; a first control circuit coupled to said second switching circuit and said desired impedance for monitoring a voltage potential of said desired impedance and for generating said second digital code based on the monitored voltage potential; and a second control circuit coupled to said first control circuit for tuning said second digital code to generate said first digital code, wherein the second control circuit comprises: an adder circuit for adding a digital code to said second digital code to generate the first digital code; a subtractor circuit for subtracting a digital code from said second digital code to generate the first digital code; and a selector circuit for selecting between said adder circuit and said subtractor circuit for tuning the second digital code to generate the first digital code.