PLL is an automatic control system adjusting controlled oscillator frequency to be equal to reference oscillator frequency multiplied by a given integer. Frequency adjustment is carried out by using negative feedback. A phase detector compares a controlled oscillator output with a reference signal. The result is a charge pump current output that supplies external feedback filter and converted to a voltage for controlled oscillator adjustment. Clock frequency divider is used to generate a signal with frequency equal to reference frequency divided into integer number.
The block is fabricated on iHP SiGe BiCMOS 0.25 um (SGB25V) technology.