Design Of Novel Fully-differential Charge Pump For PLL

With the development of wireless communication, PLL (Phase-Locked Loop) is widely used in various kinds of electronic productions, simultaneously which requests better performance PLL. What people need is the PLL with high-frequency, low-voltage, low-power dissipation, low-noise, high-stability. Among various PLLs, CPPLL (Charge-Pump Phase- Locked Loop) become current PLL products mostly for its little phase-offset and large acquisition range.Charge pump is a kind of usage electric charge to produce the high-handed electric circuit at the backlog in the electric capacity( high in power supply electric voltage) . In lock mutually the wreath PLL electric circuit, the main function of the electric charge pump is to be PFD's the numerical signal(the UP and DW) of the machine output's is converted in to imitate the signal to control to press to control to flap to concuss the machine(VCO) of frequency. When the PFD give a high accuracy mutually an error margin, the electric charge pump electric circuit has to the whole function of wreath road decisive function, namely the PLL target later even if pimping motions of the exportation electric voltage of the electric charge pumps all will cause the VCO exportation frequency to tremble to move, thus leading to go into the noise. The traditional electric charge pumps the electric circuit to exist the electric charge to reveal, the steady long exportation electric voltage scope does not greatly wait the blemish.A new novel fully-differential charge pump for PLL was designed in this paper, and differential input and differential output was used in this circuit. The way of differential input and differe- ntial output may eliminate the noise for leakage current and charge/discharge current mismat- ches, and increase the speed of circuit and the range of output voltage, and decrease and the power dissipation.The circuit was simulated by the Spectre in Cadence with CMOS 0.18μm process. When the voltage source is 1.8V, together with the current of 50μA and the frequency of 500MHz, it is shown that the range of output voltage is -1.8V~+1.8V, and the power dissipation is 0.15mW.