Title:
SEMICONDUCTOR INTEGRATED CIRCUIT DEVICE
Document Type and Number:
Japanese Patent JP3323101
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To realize a PWM f converter of high precision and a low cost by taking the power source of a filter circuit and a circuit concerning the CR time constant of an oscillation circuit part from the same power source so as to improve a pulse width modulating system(PWM) signal of high resolution without deteriorating resolution by the part of a frequency.
SOLUTION: A filter circuit part 1005 filters a PWM signal fin 1004 by the CR time constant. A comparator 1007 compares a signal obtained by holding the peak voltage of the signal filtered by a peak hold circuit part 1006 and a signal operating by the CR time constant of an oscillation circuit part 1002. An output terminal 1010 outputs the PWM signal whose output f out is frequency-converted from the comparator 1007. A power source Vdd and GND concerning the CR time constant of the filter circuit 1005 necessitated to be the same as a power source Vdd and GND also concerning the CR time constant of the oscillation circuit part 1002. In addition a precise Vref power source, etc., can be prepared inside to take from it for sharing.
Inventors:
Yutaka Saito
Koei Ozaki
Toshiaki Narukawa
Koei Ozaki
Toshiaki Narukawa
Application Number:
JP12759297A
Publication Date:
September 09, 2002
Filing Date:
May 16, 1997
Export Citation:
Assignee:
Seiko Instruments Inc.
International Classes:
H03K7/08; H03K11/00; (IPC1-7): H03K11/00; H03K7/08