Patent 7365593 was granted and assigned to Xilinx on April, 2008 by the United States Patent and Trademark Office.
A charge pump circuit has a charge pump section and a replica charge pump section. The replica charge pump section produces a replica voltage at which the UP current will match the DOWN current. A comparator compares the replica voltage to the output voltage, and adjusts the bias to the charge pump section and replica charge pump section so that the voltage level produced by the replica charge pump section matches the output voltage.