JPS649376A - Timing calibration system - Google Patents

Abstract

PURPOSE:To shorten the executing time of calibration and to make it possible to perform highly accurate timing calibration, by using the same device for a DA converter, which converts a time difference into a digital (D) value, and for a DA converter, which converts a time value for setting a delay time into an analog (A) voltage value. CONSTITUTION:At first, a delay time for a switch circuit 6 is obtained as a time difference with respect to a reference clock in a phase comparator 14. The time difference is converted into a D value. Namely, the time difference with respect to the reference clock, which is obtained in the comparator 14, is converted into a DC voltage. A D input value of a DAC 17 is controlled so that the DC voltage and the A output of a DA converter (C) 17 become equal. The output of the time difference from comparator 14 undergoes D conversion. When the time difference correction is set, the D value obtained by the D conversion of the delay time is added to the correcting value. The result is inputted into the DAC 17 as the D value. A variable D delay circuit 4 is controlled so that the A output of the DAC 17 agrees with the DC voltage, which is obtained by converting the output of the comparator into the DC voltage. Thus the time difference correction is set.