Matsushita Electric Industrial Co., Ltd.

Panasonic Corporation

Socionext Inc.

Matsushita Electronic Industrial Co., Ltd

Seiji Watanabe

Shinichi Yamane

Yoshinori Miyada

Shiro Dosho

Takahiro Bokui

Kazuhiko Nishikawa

Takashi Oka

Shiro Sakiyama

Yusuke Tokunaga

Tsuyoshi Ebuchi

Naoshi Yanagisawa

Hiroshi Koshida

Tetsuo Arakawa

Haruhisa Takata

Disclosed herein is a signal potential converter which may perform high-speed operation and which may still maintain intended signal amplitude and operate normally even while operating at a low rate or receiving a burst signal. In this signal potential converter, a capacitor receives an input signal CIN at one terminal thereof and has the other terminal thereof connected to a terminal node. A clamp circuit defines a potential at the terminal node, i.e., a signal IN, within the range of a first potential to a second potential. If a potential at the terminal node is higher than a third potential, a voltage holder circuit operates to raise the potential at the terminal node. If the potential at the terminal node is lower than the third potential, the voltage holder circuit operates to lower the potential at the terminal node.

Signal potential converter

In a signal potential converter, a capacitor receives an input signal CIN at one terminal thereof and has the other terminal thereof connected to a terminal node. A clamp circuit defines a potential (signal IN) at the terminal node within the range of a first potential to a second potential. The clamp circuit includes a level adjuster circuit configured to adjust at least one of the first and second potentials according to a supply voltage of a circuit that drives the input signal CIN.

A phase adjustment circuit includes first to nth two-phase adjustment circuits. Each two-phase adjustment circuit includes a first logic circuit for performing logical sum of two input signals, a second logic circuit for performing logical product of the two input signals, a first delay circuit having a signal delay equal to that of the second logic circuit and configured to delay a signal output from the first logic circuit, and a second delay circuit having a signal delay equal to that of the first logic circuit and configured to delay a signal output from the second logic circuit. Two signals output from two of the two-phase adjustment circuits in a certain stage are input into one of the two-phase adjustment circuits in the next stage.

Phase adjustment circuit

A multi-phase oscillator includes a plurality of ring oscillators () each having a plurality of output ports and each formed by connecting an odd number of inverters () in a ring, and a plurality of resistance elements () coupling the output ports between the plurality of ring oscillators () so that all of the plurality of ring oscillators () operate at an identical frequency while keeping a desired phase relationship. The number of the ring oscillators () is not limited to an odd number but may be an even number. The multi-phase oscillator changes the state of a succeeding node of a phase coupling to accord with the state of a preceding node of the phase coupling by using the resistance elements () as phase coupling devices. If resistors are used as the resistance elements (), the phase output accuracy greatly improves and high frequency oscillation is possible.

Multi-phase oscillator

In a voltage controlled oscillation circuit including a cascade connection of a voltage-to-current conversion circuit () for generating an input voltage converted current which is a current corresponding to an input voltage and a current controlled oscillation circuit () of which an oscillation frequency varies according to the input voltage converted current, the voltage-to-current conversion circuit () includes a first current source for outputting a current in proportion to the input voltage and a plurality of second current sources for outputting a current in proportion to a voltage obtained by shifting the input voltage. Then, a current obtained by adding a current output from the first current source and currents output from the plurality of current sources is output as the input voltage converted current to the current controlled oscillation circuit ().

Voltage controlled oscillation circuit

A PLL circuit comprises a frequency comparator for detecting a phase difference based on a difference in frequencies between a reproduced data pulse and a clock generated by a VCO; a phase comparator for detecting a difference in phases between the reproduced data pulse and the VCO clock; a selector for selectively outputting a signal supplied from the frequency comparator, a first charge pump for increasing/decreasing the output voltage on the basis of the output from the selector; a second charge pump for increasing/decreasing the output voltage on the basis of the output from the phase comparator; a loop filter for eliminating unnecessary components included in a signal obtained by adding the output from the first charge pump and the output from the second charge pump; and a VCO for generating a clock of a frequency corresponding to the output voltage of the loop filter. In this PLL circuit, when the phase difference between the reproduced data pulse and the VCO clock is within the pull-in range of the phase comparator, the operation of the frequency comparator is restricted by the output of the phase comparator. Therefore, the PLL circuit can perform stable data reading even when the reproduced data pulse has a large amount of clock jitter.

Phase locked loop circuit

This invention relates to a phase-locked loop circuit and a data reproduction apparatus, which can reduce a processing time that is required for initial adjustment in the data reproduction apparatus. In a digital data reproduction apparatus having two control functions, i.e., phase and duty adjustments for binarized data, the phase comparison with one edge is performed only at the phase adjustment by means of a phase-locked loop circuithaving an edge switching meanswhich controls the phase comparator. The phase comparatorinputs the binarized and a bit synchronous clock, and switches the output between a comparison result with one edge, i.e., a rising edge or a falling edge of binarized data, and a comparison result with both edges.

Phase-locked loop circuit and data reproduction apparatus

A PLL circuit comprises a frequency comparator for detecting a phase difference based on a difference in frequencies between a reproduced data pulse and a clock generated by a VCO; a phase comparator for detecting a difference in phases between the reproduced data pulse and the VCO clock; a selector for selectively outputting a signal supplied from the frequency comparator; a first charge pump for increasing/decreasing the output voltage on the basis of the output from the selector; a second charge pump for increasing/decreasing the output voltage on the basis of the output from the phase comparator; a loop filter for eliminating unnecessary components included in a signal obtained by adding the output from the first charge pump and the output from the second charge pump; and a VCO for generating a clock of a frequency corresponding to the output voltage of the loop filter. In this PLL circuit, when the phase difference between the reproduced data pulse and the VCO clock is within the pull-in range of the phase comparator, the operation of the frequency comparator is restricted by the output of the phase comparator. Therefore, the PLL circuit can perform stable data reading even when the reproduced data pulse has a large amount of clock jitter.

This invention relates to a phase-locked loop circuit and a data reproduction apparatus, which can reduce a processing time that is required for initial adjustment in the data reproduction apparatus. In a digital data reproduction apparatus having two control functions, i.e., phase and duty adjustments for binarized data, the phase comparison with one edge is performed only at the phase adjustment by means of a phase-locked loop circuit having an edge switching means which controls the phase comparator . The phase comparator inputs the binarized and a bit synchronous clock, and switches the output between a comparison result with one edge, i.e., a rising edge or a falling edge of binarized data, and a comparison result with both edges.

The successive comparison analog-to-digital (A-D) converter includes a plurality of capacitors, a plurality of first analog switches, a plurality of second analog switches, a plurality of third analog switches, a voltage comparator, and a state controller. Each of the plurality of capacitors has a capacitance weighted with a prescribed weighting factor. Each of the plurality of first analog switches has an on-state resistance weighted with a prescribed weighting factor. In the successive comparison A-D converter, a first analog switch corresponding to a capacitor having a capacitance weighted with a larger weighting factor has an on-state resistance weighted with a smaller weighting factor, whereby a time constant for this capacitor can be reduced. As a result, the difference in time constant between the capacitors is reduced. This enables reduction in time required to precharge (sample and hold) an analog input, improving the A-D conversion speed.

Successive comparison analog-to-digital converter

A jitter detector obtains a phase difference between input signals as a digital value to make jitter between the signals easily detectable. The jitter detector includes comparison pulse generator, periodic signal generator, counter and arithmetic unit. The comparison pulse generator outputs one phase difference comparison pulse after another. Each phase difference comparison pulse has a width representing the phase difference between first and second input signals. The periodic signal generator outputs a periodic signal every time a value obtained by accumulating the widths of the phase difference comparison pulses exceeds a predetermined value. Receiving the periodic signal and a clock signal with a period shorter than that of the periodic signal, the counter counts the number of pulses of the clock signal during one period of the periodic signal and outputs a resultant count. And the arithmetic unit detects and outputs a variation in the count as jitter between the first and second input signals.

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Kyoto, Japan

Seiji Watanabe