| 摘要 |
<p>PURPOSE:To decrease a minimum operating voltage and to enhance voltage accuracy by combining a voltage detection circuit detecting large dispersion in its detected voltage and providing a pulse without fail at application of power whose minimum operating voltage is low and a band gap reference voltage generating circuit utilizing the output pulse to be operated normally even in the presence of rapid power supply fluctuation. CONSTITUTION:At application of a power supply VDD, a power supply voltage detection circuit 17 used for the power-on reset circuit of a microcomputer provides an output of a high level pulse without fail even when a voltage of the power supply VDD rises slowly or rises steeply. The pulse is an input 23 to a band gap reference voltage generating circuit 18 via a delay circuit 19 and an EXOR 20 and a current flows to the circuit 18 as an initializing current at application of power and the normal operation is started. After an output 12 of the circuit 18 is made stable, its output voltage is compared with the voltage of the power supply VDD divided by resistors R5, R6 to decide a voltage detection level. Thus, the voltage detection in the circuit operation is set highly accurately.</p> |
