Miscellaneous active electrical nonlinear devices – circuits – and – Specific signal discriminating without subsequent control – By amplitude
Reexamination Certificate
2000-02-28
2001-05-08
Tran, Toan (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific signal discriminating without subsequent control
By amplitude
C327S143000, C327S072000
Reexamination Certificate
active
06229352
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of level detection circuitry and in particular to circuitry for detecting the level of an input signal, such as a power supply voltage, which is also powered by the input signal.
2. Background of Related Art
Most electronic systems contain storage elements which have indeterminate states when the primary power source for the system is first applied or when the power source drops below some minimum operating level. Accordingly, it is often necessary to provide some means whereby the storage elements are set to a known state at initial power on or after a power drop. Such circuits are sometimes referred to as power on reset circuits.
One difficulty in implementing power on reset circuits is that such circuits must often be powered by the same voltage source that is monitored by the circuit. This can present a challenge, particularly if the circuit must ensure that the system is in a proper initial state at relatively low supply voltages. Furthermore, such reset circuits must operate reliably when the input supply voltage either has a very fast rise time or a slow rise time.
The present invention is capable of detecting input signals, such as power supply voltages, while being powered by such input signals. The input signal level is reliably and accurately detected and an output is provided to accommodate input signals having fast and slow rising inputs. These and other advantages of the present invention will be apparent to those skilled in the art upon a reading of the following Detailed Description of the Invention together with the drawings.
SUMMARY OF THE INVENTION
A level detection circuit for producing an detection output when an input signal reaches a predetermined level is disclosed. Typically the input signal is the primary power supply voltage of an electronic system reset by the detection circuit output at power on and at low power supply voltages. The detection circuit includes a voltage reference circuit means for producing a reference voltage having a magnitude which is relatively independent of the input signal magnitude once the input signal has reached a first operating voltage.
The level detection circuit further includes translator circuit means for producing a translated voltage having a magnitude which is indicative of the magnitude of the input signal. Preferably, this element includes a series-connected MOS transistor and a resistor, with the output of the translator circuit means being produced at the junction of these two devices. A comparator means is provided for comparing the reference voltage and the translated voltage and for producing a comparator output based upon the comparison. The comparator means is powered by the input signal. The remaining elements of the subject detection circuit are also typically powered by the input signal. In addition, output means is used for producing the detection output signal in response to the comparator output. The output means preferably includes some form of pulse shaping circuitry such as an inverter followed by a one shot circuit.
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Briner Michael S.
Chevallier Christophe J.
Roohparvar Frankie F.
Micro)n Technology, Inc.
Schwegman Lundberg Woessner & Kluth P.A.
Tran Toan
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