Patent ID: 7427936
Filing Date: 2008-09-23
Classification: H03M

Abstract:
1. An A/D converter device comprising: a plurality of input lines connected, through a pull-up resistor or a pull-down resistor, to a first power supply line selected from a positive-side power supply line connected to a positive side of a DC power source and a negative-side power supply line connected to a negative side of said DC power source; a multiplexer having an input signal selection switch device for selecting, as an A/D conversion object, one of sensor signals outputted from external sensors each of which is connected to a corresponding one of said input lines, and delivering said A/D conversion object to a signal transfer line connected to said multiplexer; a sample-hold section connected to said signal transfer line through an input switch device to hold therein said A/D conversion object; an A/D converting section A/D converting said A/D conversion object held in said sample-hold section into digital data representing a signal level of said A/D conversion object; an initialization switch device being turned on to connect a connection node between said input switch device and said sample-hold section to said first power supply line to initialize said sample-hold section; and an A/D conversion control section controlling said multiplexer such that said sensor signals are successively taken in as said A/D conversion object in a predetermined A/D conversion cycle, and alternately turning on and off said initialization switch device and said input switch device in synchronization with said A/D conversion cycle in order that initialization of said sample-hold section, sampling operation by said sample-hold section, and A/D converting operation by said A/D converting section are performed successively; wherein said multiplexer is provided with a reference-voltage-selection switch device being turned on to apply reference voltage to said signal transfer line, and wherein said A/D converter device further comprises a comparing section comparing a voltage of said signal transfer line with a predetermined abnormality judging voltage, and an abnormality judging section configured to turn on said reference-voltage-selection switch device in order to apply said reference voltage to said signal transfer line in synchronization with said A/D conversion cycle on condition that said A/D converting operation by said A/D converting section is not interrupted, and to determine presence of abnormality in said A/D converter device if an comparison result of said comparing section does not match an expected value corresponding to said reference voltage when said reference-voltage-selection switch device is turned on.