We present a custom digital architecture that implements the Constant Range algorithm for nonuniformity correction of infrared focal plane arrays. This scene-based technique uses the statistics of the acquired video stream to compensate the gain and offset nonuniformity of the infrared imager online. We evaluate the performance of our architecture while processing raw infrared video at 60 frames per second, with a resolution of 640x480 14-bit pixels. Our implementation of the Constant Range algorithm on a Xilinx Spartan-6 LX45 FPGA uses 1.8% of logic and 26% of arithmetic resources of the chip, consuming only 29.5mW of power.