Patent ID: 7253656

Claim:
A calibration circuit of a driver control circuit controlling a plurality of input/output drivers of an integrated circuit, comprising: an external resistor having a resistance corresponding to the resistance of an output line of said integrated circuit; said external resistor having a first terminal and a second terminal which is connected to ground; a first voltage/current converter being connected to said first terminal of said external resistor forming a first node and being connected to a supply voltage, so that a reference voltage in respect to ground appears at said first node; a first comparator configured to compare said reference voltage with a voltage having half the value of said supply voltage in order to generate a first amplified differential voltage which is converted by said first voltage/current converter into a first current, so that said first voltage/current converter regulates the reference voltage to half the value of said supply voltage; a second voltage/current converter, which is connected via a second node to a pull-down driver and converts said first amplified differential voltage into a second current being substantially identical to said first current, in order to set the pull-down driver voltage of said pull-down driver to half the supply voltage; a second comparator comparing said reference voltage with said pull-down driver voltage in order to provide a first calibration signal at the output of said second comparator; a voltage/current converter circuit, which is connected to a pull-up driver via a third node and converts said first amplified differential voltage into a third current having the negative value of said first current, in order to set the pull-up driver voltage of said pull-up driver to half the value of said supply voltage; and a third comparator, which compares said reference voltage with said pull-up driver voltage in order to provide a second calibration signal at the output of said third comparator.