Apparatus for automatically selecting the internal or external resistor

摘要

The present invention relates to an apparatus for automatically selecting an internal or external resistor, characterized by that a built-in control unit is placed in the front of the oscillator of the integrated circuit, and such control unit comprises a detection circuit for coupling the external resistor and oscillator, and an internal resistor bridging the detection circuit in parallel with its output end such that the detection circuit can automatically detect whether or not there is any input of serial signal from the external resistor to switch into the external or internal resistor at appropriate time, and further select inputting the optimal operating frequency of the control IC.