Patent ID: 8693048

Claim:
A switchable ROS driver circuit for an electrophotographic system for selective switching between a plurality of system printing speeds, comprising: a sub-pixel clock generator for generating output signals applied to laser drivers in a raster output scanner (ROS), the sub-pixel clock generator including: a phase locked loop circuit including a charge pump circuit and a loop filter for communicating a charge pump current to a voltage controlled oscillator (VCO) and setting a frequency of the VCO for controlling printing speeds of the electrophotographic system; a clamping circuit disposed between the charge pump and loop filter circuits and maintaining the voltage communicated to the VCO between predetermined limits corresponding to first and second printing speeds, the clamping circuit clamping a voltage to the VCO in a range that settles jitter caused by changes in the charge pump current when a printing speed is adjusted; and an ROS light source in operative communication with the sub-pixel clock generator for sub-pixel control of the ROS light source, the ROS light source including: at least one laser driver generating an image exposure on a photoconductor surface by energizing a laser beam at laser pulse durations each based on the frequency of the VCO; wherein the ROS light source adjusts the laser pulse durations based on a signal received from the sub-pixel clock generator, the signal being based on a value of an image data byte.