| 摘要 |
PROBLEM TO BE SOLVED: To provide an impedance adjustment circuit having a reduced circuit scale. SOLUTION: The impedance adjustment circuit is provided with: an externally attached resistor 3; a comparator 2 for comparing the magnitude in resistance values of a replica resistor 4, constituting a replica of the resistor 5 to be adjusted; and a resistance control circuit 10. The resistor control circuit 10 is provided with: a replica resistor control counter 11 for increasing/decreasing a count value based on a result of comparison of the comparator 2 and outputting a control signal to the replica resistor; an adjusted resistor control signal holding circuit 12 for holding a control signal to be given to the resistor 5 to be adjusted; and a monitoring circuit 13 for receiving the state of the counter and the output of the holding circuit, and supplying an output (Y) of the adjusted resistor control signal holding circuit 12 as an input (Z) to the adjusted resistor control signal holding circuit 12, when the difference (¾X-Y¾) in value between the count state of the replica resistor control counter 11 and the output (Y) of the adjusted resistor control signal holding circuit 12 lies within a predetermined range. COPYRIGHT: (C)2009,JPO&INPIT
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