| 摘要 |
PURPOSE:To obtain a lock detection circuit setting accurately a nondetection time of unlocking by setting a nondetection time of unlocking state to a proper value after the manufacture of an IC in a lock detection circuit. CONSTITUTION:Capacitors 743-746 are constituted by plural number of capacitors Ca connected in parallel and the relation of Cm:C2:C1:C0=m:4:2:1 exists. The total capacitance C of a variable capacitor 4 is expressed as (m+n)Ca (0<=n<=7), a nondetection period tau of unlock is proportional to the total capacitance C and the relation of tau=(m+n/m+7)taumax is obtained. Then the time taumax is obtained by measuring the unlock nondetection period in the initial state by a ROM 12 and the tau is set to the ROM 12 by writing a proper value at an interval of taumax/m+7 as an optimum value. |
