Patent US 6,975,159

A method of operating a memory system that includes an integrated circuit memory device is provided. A value representing an output voltage setting of an output driver of the memory device is stored in a register. The output driver outputs the drive voltage. A signal derived from the drive voltage is compared to a reference signal to generate a signal that indicates an adjustment to the output voltage setting. The output voltage setting of the output driver is adjusted using a counter that holds a count value representing an update to the output voltage setting. The count value is updated in accordance with a signal that indicates the adjustment to the output voltage setting.