Apparatus to remove the loop filter resistor noise in charge-pump PLL

A loop filter and resistor technology, applied in the direction of electrical components, automatic power control, etc., can solve problems such as increasing switching noise and increasing loop filter area.

Active Publication Date: 2013-08-21
TEXAS INSTR INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, there appear to be three disadvantages to this structure: 1) there is a need for additional capacitors and may increase the overall loop filter area by 15%, 2) non-overlapping clock generators are required to generate the control signals for switching capacitors, 3) Two large switches are required for the switched capacitor network (Klemmer patented Figure 4 Q1 and Q2 in ), this will add some switching noise at the 'VCTRL' node due to the connection through the parasitic capacitor

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  • Apparatus to remove the loop filter resistor noise in charge-pump PLL
  • Apparatus to remove the loop filter resistor noise in charge-pump PLL
  • Apparatus to remove the loop filter resistor noise in charge-pump PLL

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Embodiment Construction

[0016] refer to figure 2 , which illustrates one aspect of a PLL with a loop filter resistor removal circuit 200 constructed in accordance with the principles of the present application. As understood by the designated inventors of this application, in a typical charge pump PLL, the loop filter resistor is one of the contributors to the overall output PLL phase noise (jitter). The loop filter resistor noise of the PLL can be reduced by using the method of removing the loop filter resistor during part of the PLL cycle.

[0017] Typically, a PLL contains two poles at the start and a high DC gain and is therefore unstable. The resistor is connected in series to the capacitor as a loop filter resistor to create a zero in the feedback loop of the PLL, which helps to stabilize the PLL. As the inventor wishes, the loop filter resistor, according to the current inventor's understanding, the adoption of the resistor Rcp155 in Fig. 1 introduces more problems in the PLL circuit, such ...

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Abstract

An improved charge pump based phase locked loop where the loop filter resistor noise is reduced by about an order is presented. The voltage controlled oscillator generates a clock signal, and this is input to the phase detector, which, compares the oscillator clock with the reference clock and using the charge pump it generates a current output proportional to the phase difference. The loop filter converts this proportional current to a voltage and connects it to the oscillator input. The loop filter consists of a capacitor, resistor and the apparatus that bypasses most of the resistor noise.

Description

[0001] priority [0002] This application requests the U.S. provisional application for the title "A NOVEL TECHNIQUE TO REMOVE THE LOOP FILTER RESISTOR NOISE IN CHARGE-PUMPPLL" filed on February 20, 2012. Priority to Application No. 61 / 600,745, the entire contents of which are incorporated herein by reference. technical field [0003] The present application relates generally to a phase locked loop (PLL), and more particularly to canceling loop filter resistor thermal noise in a PLL. Background technique [0004] Referring to FIG. 1 , a conventional PLL 100 is shown. Resistor Rcp155 is used in PLL 100 for stability purposes to create a "zero" in the loop switching function and ensure stability around the overall gain frequency. However, the overall phase noise (jitter) of the PLL can be problematic. [0005] Other methods of solving various problems of PLL loops, such as phase noise characteristics, have been proposed, such as Klemmer's U.S. Patent No. 6,420,917B1, entitl...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03L7/089H03L7/093
Inventor R·帕瓦
Owner TEXAS INSTR INC
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