Won Hyo Lee Jun Dong Cho Sung Dae Lee A High Speed and Low Power Phase-Frequency Detector and Charge - pump. 269-272 1999 conf/aspdac/1999 ASP-DAC http://csdl.computer.org/comp/proceedings/asp-dac/1999/2329/00/23290269abs.htm db/conf/aspdac/aspdac1999.html#LeeCL99a