Reset circuit
OwnerRoger E. Susiinventor
Life of this patent
Estimating the term…
Abstract
A reset circuit which monitors the voltage of the power supplied to a microprocessor unit, and produces a low resistance to ground at the reset terminal of the microprocessor whenever the supply voltage changes from a low value to a high value, or from a high value to a low value. It is based upon the combination of two RC circuits of different time constants, such that when the supply voltage is constant, no current flows in these circuits. A transistor is connected to the RC network such that it carries current only when there is a changing voltage of the power supply. If the voltage increases or decreases, a second transistor acting as an electronic switch grounds the reset terminal, and when the voltage becomes constant again, either at a high value or a low value, the switch opens and the reset voltage goes high.
Claims4
A reset circuit for monitoring the power supply voltage of a microprocessor, and for disabling the action of said microprocessor for a selected time period, at the times of power supply voltage change, such as at times of power on and power off of the microprocessor, comprising:
- (a) a bridge network having four terminals, a first terminal A, a second terminal B, a third terminal C and a fourth terminal D, a first arm comprising a first diode D1 connected from terminal A to terminal B, a second arm comprising a first capacitor C2 connected from terminal B to terminal C, a third arm comprising a second capacitor C1 connected from terminal C to terminal D, and a fourth arm comprising a first resistor connected from terminal A to terminal D;
- (b) a power supply with voltage terminal V connected to terminal A and a ground terminal connected to terminal C;
- (c) the output terminals of said bridge are terminals B and D, with a load resistance R2 connected between them;
- (d) amplifier means connected across the output terminals B and D, said amplifier means having no direct connection to said power supply and receiving operating power only from said bridge when said bridge is unbalanced;
- (e) a reset terminal;
- and
- (f) an electronic switch means controlled by said amplifier means and being connected to said reset terminal, the switch means supplying a high voltage which serves as a reset voltage, when said amplifier means is turned off.
Dependencies are inferred from the claim text.