JITTER MEASURING METHOD, JITTER MEASURING CIRCUIT AND OSCILLATION CIRCUIT EQUIPPED WITH IT

摘要

PROBLEM TO BE SOLVED: To provide a method for facilitating jitter measurement of an oscillation circuit assembled in a semiconductor integrated circuit.;SOLUTION: A DLL circuit 10 is constituted of a VCDL11 outputting a delay output Sout1 in which signal to be measured Sin is delayed for one period, a phase comparator 12 for phase-comparing between the signal to be measured Sin and the delayed output Sout1, a charge pump 13 for converting the output of the phase comparator 12 to the current signal of a pulse width corresponding to the phase difference, and a low-pass filter for gaining the output of the charge pump 13 as the input and controlling the delayed time of VCDL11 in accordance with the output. In a state that the DLL circuit 10 is locked, the output of the phase comparator 12 is converted to a pulse width current signal according to the phase difference by the charge pump 21 and is integrated with an integration circuit 22. The integrated output Sinteg is made a value corresponding to the jitter and when this is over a reference voltage Vref, the jitter is judged to have exceeded an allowance range.;COPYRIGHT: (C)2005,JPO&NCIPI