Phase locked loop circuit

Abstract

Abstract PURPOSE:To keep normal operation even in a digital processing circuit by resetting an integration value in an integration type loop filter when an output voltage of the integration type loop filter exceeds a prescribed threshold level. CONSTITUTION:A deciding circuit 4 detects an output voltage VC of an integration loop filter being a control voltage of a voltage controlled oscillator 3, the output voltage VC is compared with a preset threshold level VA and an information signal representing a fact of the output voltage in excess of the threshold level is outputted to an averaging circuit 5 in case of ¦VC¦>VA. Then a reset signal is outputted from the averaging circuit 5 to the integration loop filter 2, the integration value in an integration device in the integration loop filter 2 is reset and integration is newly started. Thus, an even the frequency of the integration loop filter output voltage in excess of the frequency of the normal synchronization range of a phase locked loop circuit is prevented. Then the normal synchronization is maintained even in a digital processing circuit, and runaway of a phase locked loop circuit is prevented.

Inventors

• 👤 Susumu Otani
• 👤 進 大谷

Bibliographic Details