Patent ID: 8488186

Claim:
A switchable raster output scanner (ROS) driver circuit for an electrophotographic system for selective switching between a plurality of system printing speeds comprising: a sub-pixel clock generator tuned to a first reference signal corresponding to a first printing system speed and including a phase locked loop circuit and a charge pump circuit, wherein the charge pump circuit charges a loop filter circuit and sets a first input voltage at a voltage-controlled oscillator (VCO), wherein the VCO to generate a desired frequency corresponding to the first system printing speed, and wherein an input voltage to the VCO is set by a loop filter circuit provided with a charge pump current output by a charge pump circuit; a control circuit associated with the sub-pixel clock generator comprising a plurality of current generators respectively disposed in parallel with the charge pump current output by the charge pump circuit for selective and incremental adjustment of the first input voltage to a second input voltage to the VCO for generating another desired frequency corresponding to a second system printing speed; and an ROS light source in operative communication with the sub-pixel clock generator for sub-pixel control of an ROS light source.