Low cost/low current watchdog circuit for microprocessor

Details Low cost/low current watchdog circuit for microprocessor Low cost/low current watchdog circuit for microprocessor

1994-11-10

1996-10-08

Voeltz, Emanuel T.

Boots, shoes, and leggings

364569, 364550, 364707, 39518508, 395750, 371 61, 371 62, G06F 1130

Patent

active

055637990

ABSTRACT:
A watchdog circuit and method are provided for monitoring a microprocessor to detect the presence of a malfunction condition such as a program lock-up. The watchdog circuit includes a first capacitor coupled to a supply voltage and a transistor having a collector and emitter coupled in parallel with the first capacitor. The transistor has a base for receiving a signal in response to a status output signal generated by the microprocessor. A voltage threshold detector is provided for comparing a voltage potential associated with the capacitor with a predetermined threshold voltage and producing a reset signal in response thereto. The threshold voltage detector produces a small current which is utilized to charge the first capacitor. The reset signal is provided to the microprocessor to initiate a reset operation which will reset the microprocessor in an attempt to eliminate the malfunction condition. Additionally, a feedback path may be provided between the output and the base of the transistor to allow for repetitive reset signals during a continuous microprocessor malfunction condition.

REFERENCES:
patent: 4879647 (1989-11-01), Yazawa
patent: 5081625 (1992-01-01), Rhee et al.
patent: 5113504 (1992-05-01), Matsuda
patent: 5203000 (1993-04-01), Folkes et al.
patent: 5345583 (1994-09-01), Davis
patent: 5426776 (1995-06-01), Erdman
patent: 5440263 (1995-08-01), Fournel et al.
MITSUMI ICs--Technical literature on Reset products by Mitsumi Electronic Corp., Inc.

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