TheTC620/TC621aresolid-statetemperaturesensors
thatareeasytoprogramandinterfacewithcontrol
equipment.TheTC620sensesthetemperatureinter-
nally,whiletheTC621usesanexternalthermistor.
Figure1showshowthedevicesareconnected.
TheTC620/TC621datasheet(DS21439)describes
howtocalculatethecorrectresistancevalueforany
desiredtemperature.Italsogivesagraphicaldepiction
oftheoutputsforvaryingtemperatures.
SincetheTC620sensestemperaturesinternally,its
outputsmustbelimitedto1mA.Thedevicecansource
orsinkhighercurrents,butinternalself-heatingmay
causeerrorsinthetemperaturesensing.TheTC621
cansourceorsink10mA,sinceitusesanexternalMAN773ApplicationCircuitsoftheTC620/TC621Solid-StateTemperatureSensorsthermistortosensearemotetemperature.InternalAuthor:MicrochipTechnologyInc.heatingwillnotaffectthetemperaturesensingaccuracy.INTRODUCTIONFigure2isaschematicofaheatingandcoolingcon-TheTC620/TC621aresolid-statetemperaturesensorstrollerusingasingleTC620andaTC4469Quadt
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