Voltage detector
AssigneeMotorola, Inc.
InventorJames S. Thomas
Life of this patent
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Abstract
An MOS low voltage detector circuit includes a comparator which compares an internally generated reference voltage with an internally generated non-linear voltage. Both the reference voltage and the non-linear voltage are derived from a supply voltage, and the comparator generates an output whenever the divided down non-linear voltage falls below the reference voltage. This output is supplied to a series of regularly biased MOS inverter stages which not only amplify the comparator output but also amplify the inherent offset error in the comparator itself. Voltage compensating means may also be included in the comparator.
Claims13
A circuit for detecting when a supply voltage falls below a predetermined value, comprising:
- first means for receiving said supply voltage and generating therefrom a first reference voltage;
- voltage dividing means coupled to said supply voltage for producing a non-linear divided voltage therefrom;
- comparing means coupled to said first means and said voltage dividing means for generating an output when said divided voltage falls below said first reference voltage;
- and
- amplifying means coupled to said comparing means for amplifying said output.
A circuit for detecting when a supply voltage falls below a predetermined value, comprising:
- first means for receiving said supply voltage and generating therefrom a first reference voltage;
- voltage dividing means coupled to said supply voltage for producing a non-linear divided voltage therefrom, comprising:
- a first field effect transistor having source, gate and drain electrodes, said drain electrode coupled to said supply voltage and said gate electrode coupled to said source electrode;
- a second field effect transistor having source, gate and drain electrodes, said drain electrode coupled to the source and gate electrodes of the first field effect transistor and coupled to the gate electrode of said second field effect transistor;
- and
- a third field effect transistor having source, gate and drain electrodes, said source electrode coupled to a second reference voltage, said gate electrode coupled to said first means and said drain electrode coupled to the source electrode of said second field effect transistor;
- comparing means coupled to said first means and to the source electrode of said second field effect transistor of said voltage dividing means for generating an output when said divided voltage falls below said first reference voltage;
- and
- amplifying means coupled to said comparing means for amplifying said output.
Dependencies are inferred from the claim text.