Voltage controlled oscillator for loop circuit

Abstract

The invention provides a loop circuit voltage control oscillator which comprises a time-delay unit in an even-number stage, wherein the same-phase input and the reverse-phase input of a common time-delay path in a time-delay unit in a first stage of the time-delay unit in an even-number stage are respectively connected with the same-phase input and the reverse-phase output of a time-delay unit in a previous stage of the time-delay unit of a first stage. The same-phase input and the reverse-phase output of the common time-delay path in a time-delay unit in every other stage are respectively connected with the reverse-phase output and the same-phase input of the time-delay unit in a pervious stage of the time-delay unit in every other stage. The input of a negative time-delay path of the time-delay unit in every stage of the time-delay unit in an even-number stage is connected with the output of time-delay units of the first two stages of the time-delay unit in every stage. The control-voltage input end and the power supply input end of the time-delay unit in every stage in the time-delay unit in an even-number stage are respectively connected with the input control voltage end of a loop circuit VCO and a DC power supply.

Description

technical field [0001] The present invention relates to a loop voltage controlled oscillator (VCO), and more particularly, to a loop VCO with low phase noise and improved output linear range. Background technique [0002] At present, PLL has a very wide application in SOC, such as clock recovery (clock recovery), frequency synthesis (frequency synthesis) and so on. As the core module of PLL, VCO also has higher and higher requirements in application. [0003] FIG. 1 is a diagram showing a circuit of a conventional basic loop VCO. [0004] Referring to FIG. 1 , the traditional basic loop VCO circuit includes: a current mirror formed by transistors MP1 and MN1 and an odd-numbered loop formed by five stages of current-controlled inverters. Each stage of the current-controlled inverter is composed of a P-type transistor and an N-type transistor. [0005] Vctrl is the control voltage of the loop VCO, the current of MN1 and MP1 is adjusted through Vctrl, and the load capacitanc...

AI Technical Summary

Problems solved by technology

When Vctrl is close to the power supply voltage, affected by the channel length modulation effect of the MOS tube, the current mirror circuit exhibits nonlinear characteristics, so Vctrl is also limited in the high-voltage region

Therefore the input range of this circuit is small

[0010] 2. Poor adjustment linearity

Therefore, the regulation linearity of the circuit is poor

[0012] 3. Low power supply voltage sensitivity

The above-mentioned basic circuit is a single-ended oscillator, which is very sensitive to power supply noise, which leads to large output jitter and poor phase noise.

[0014] CMOS ring oscillators are widely used in loop VCOs due to their advantages of easy integration, large adjustment range, small layout area, and low power consumption, but poor noise performance has always been a drawback

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