| 摘要 |
A frequency control and phase control for a voltage controlled oscillator (50) of a phase synchronizing circuit (100) comprise the current paths of two systems. A frequency control system comprises a filter (75) which converts an impulsive output current (i1) of a charge pump (70) driven by phase error signals (X1, X2) into a DC voltage, and a resistor (R1 or R2) which converts the DC voltage into a DC current (i3). The phase control system comprises a charge pump (80) which generates an impulsive output current (i2) from the phase error signals (X1, X2). The frequency and phase of an oscillation output (VOUT) of the voltage controlled oscillator (50) are controlled by a synthesized current (i4) which is the sum of the DC current (i3) and output current (i2). When the data transfer rate of an input signal (SIN) is changed, it is possible, by varying the values of the currents (i3, i2) through the switchover of switches (SW1, SW2), to make a natural angular frequency proportional to the transfer rate, keeping a dumping coefficient unchange. Thereby, a phase synchronism corresponding to the data transfer rate of a wide range can be realized. |
