Abstract: A current source calibration circuit and methodology reduce noise generated by current switching. In one embodiment, the calibration circuit provides a random or pseudo-random clock signal to control a switching of calibration circuit. A clock signal generator has been described that provide a number of clock signals having different phases. In one embodiment, the clock signals are used to select a current source of a DAC for calibration. By using a random clock to select the current source, noise, which is generated by switching a primary current source with a backup current source, is spread out over a wider frequency range.