Power on reset circuit and one chip microcomputer using same

Details Power on reset circuit and one chip microcomputer using same Power on reset circuit and one chip microcomputer using same

1996-06-13

1999-07-27

Callahan, Timothy P.

Miscellaneous active electrical nonlinear devices, circuits, and

Signal converting, shaping, or generating

Synchronizing

327198, H03L 700

Patent

active

059296720

ABSTRACT:
A power-on reset circuit incorporated in a semiconductor device, such as a one-chip microcomputer, includes a first capacitor and a second capacitor each having one of its electrodes grounded, a first switch circuit connecting the other electrode of the first capacitor to a voltage source, a second switch circuit connecting the electrode of the first capacitor connected to the voltage source to the other electrode of the second capacitor, a voltage detecting circuit which outputs a reset-releasing signal when the voltage of the second capacitor reaches a specified voltage level, and a discharge circuit having a first resistor and a diode connected in series between the second capacitor and the voltage source for discharging the second capacitor when the source voltage drops. There may further be provide an integrating circuit having a second resistor connected to the voltage detecting circuit and a third capacitor, an output circuit connected to the integration circuit and having a hysteresis characteristic and a third resistor connected between the second capacitor and the second switch circuit. A reset circuit thus structured can dependably output a reset signal at power-on but does not output such a reset signal when the source voltage drops momentarily during a normal operation for a time duration shorter than a specified short length of time.

REFERENCES:
patent: 4528629 (1985-07-01), Breitling
patent: 4591745 (1986-05-01), Shen
patent: 4607178 (1986-08-01), Sugie et al.
patent: 4611126 (1986-09-01), Miller
patent: 4614880 (1986-09-01), Go et al.
patent: 4886984 (1989-12-01), Nakaoka
patent: 5479132 (1995-12-01), Verhaeghe et al.
patent: 5578951 (1996-11-01), Lee et al.
patent: 5721502 (1998-02-01), Thomson et al.

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