Double-loop filtering phase-locked loop circuit

Abstract

The invention discloses a double-loop filtering phase-locked loop circuit, comprising a phase detector, a double-way charge pump and a loop filtering unit which are connected in series to form a loop. The circuit also comprises a voltage and current conversion and current addition circuit unit, a current control oscillator and a frequency divider. An input end of the phase detector is connected with a reference clock signal end; the voltage and current conversion and current addition circuit unit is used for converting control voltages output by the double-way charge pump and the loop filtering unit into currents; and an output end of the frequency divider is connected with a feedback input end of the phase detector. Compared with related technologies, the double-loop filtering phase-locked loop circuit provided by the invention has the advantages that the circuit is simple in structure, low in cost, low in power consumption and high in stability.

Description

【Technical field】 [0001] The invention relates to the field of electronic circuits, in particular to a phase-locked loop circuit used for double-loop filtering of a circuit clock system. 【Background technique】 [0002] In the application of integrated circuits, the clock system is an important module of chip design. In order to meet the different clock needs of the system, it is realized by using a phase-locked loop circuit. [0003] The phase-locked loop circuit of the related art mainly includes a phase detector, a charge pump, a loop filter, a voltage-controlled oscillator and a frequency divider. [0004] However, in the PLL circuit of the related art, the loop filter includes a resistor, a first capacitor, and a second capacitor, the resistor and the first capacitor are connected in series and grounded, and the second capacitor is grounded and connected to the The resistors are connected in parallel. For the stability of the system, the first capacitor needs to be man...

AI Technical Summary

Problems solved by technology

For the stability of the system, the first capacitor needs to be many times larger than the second capacitor, and the size of the first capacitor is several hundred pF or even nF level, and the capacitor of this capacity level needs to be occupied when it is implemented in an integrated circuit. Relatively large chip area increases the cost of the chip

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