Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Synchronizing
Reexamination Certificate
1999-01-28
2001-03-06
Callahan, Timothy P. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Synchronizing
C327S198000
Reexamination Certificate
active
06198318
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to electronic circuitry, and, more particularly, to a method and apparatus for providing a power-on-reset signal during periods of time when the power supply is activated, and/or when the voltage level of the power supply falls below a predetermined voltage level.
2. Description of the Related Art
In electronic circuits, such as CMOS or bipolar circuits, involving sequential logic design, it is often useful to initialize the states of logic elements, such as flip-flops, latches, counters, etc., to a known value when the power supply to those elements is turned on. It is also desirable to reset the states of such elements to a known value when a glitch occurs on the power supply or when the supply voltage falls below a certain threshold value. This reset signal is then turned off when supply voltage reaches a specified value. This operation is performed by what is commonly called a power-on-reset circuit
A desirable power-on-reset circuit should be capable of providing a reliable reset state of sufficient duration either on power-up or when the supply voltage falls below a specified threshold value, and this reset operation should be independent of the rise and fall time of the supply voltage. Further, the power-on-reset circuit should consume minimal static current and be easy to implement in existing technologies.
The present invention is directed to providing all of the above features.
SUMMARY OF INVENTION
In one aspect of the present invention, an apparatus is provided for controlling a reset function of an electronic device. The apparatus includes a circuit adapted to monitor a system voltage level and deliver a control signal in response to the system voltage level falling below a preselected value. A duration controller is adapted to receive the control signal and deliver a first reset signal a preselected duration of time after receiving the control signal. A voltage level controller receives the reset signal. The voltage level controller passes the reset signal in response to the system voltage being greater than a preselected magnitude.
In another aspect of the instant invention, a method is provided for controlling a power-on-reset signal in response to a system voltage level being below a preselected level. The method includes: delivering a control signal indicative of a system voltage level being below a preselected level; receiving the control signal and delivering a reset signal after a preselected period of time; and receiving the reset signal and passing the reset signal in response to the system voltage level being greater than a preselected magnitude.
REFERENCES:
patent: 4902907 (1990-02-01), Haga et al.
patent: 5039875 (1991-08-01), Chang
patent: 5302861 (1994-04-01), Jelinek
patent: 5394104 (1995-02-01), Lee
patent: 5534804 (1996-07-01), Woo
patent: 5552725 (1996-09-01), Ray et al.
patent: 5917255 (1999-06-01), Ciccone
Bhaskaran Suraj
Kozhumam Shankar R.
Nair Vijayakumaran V.
Callahan Timothy P.
Englund Terry L.
Legerity Inc.
Williams Morgan & Amerson
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