| 摘要 |
A low voltage detection circuit is provided to use an A/D(Analog To Digital) converter embedded in a microcomputer to detect the drop of power voltage at high precision, thereby making the circuit size small and precisely detecting lowering of voltage of a power supply. A low voltage detection circuit comprises a reference voltage generating circuit(14) for outputting reference voltage(Vref) which does not depend on power voltage(Vdd) and an A/D converter(32) for converting the reference voltage into a digital value, and detects the power voltage on the basis of the digital value output from the A/D converter. The A/D converter is composed of a ladder resistor generating plural divided voltages by dividing the power voltage; a comparator comparing the reference voltage and divided voltage; and a control circuit selecting the divided voltage according to the comparison result of the comparator.
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