US 4,365,174 AGranted

Pulse counter type circuit for power-up indication

AssigneeRCA Corporation

InventorNicholas Kucharewski

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Abstract

A circuit for counting pulses which may be used, for example, to provide a power on reset signal after power is applied to a circuit, employing charge transfer between two capacitors. The counter charges a first capacitor to a first voltage level between input pulses. During each input pulse, a portion of the charge stored on the first capacitor is transferred to the second capacitor. The voltage across the second capacitor increases with each input pulse. When the voltage on the second capacitor reaches a predetermined threshold level, an output signal is provided by a threshold detector to indicate that a predetermined number of input pulses has been counted. The second capacitor is then discharged in order to reset the pulse counter before beginning another counting cycle.

Claims6

Dependent claims

A pulse counter type power-up circuit providing an output indication delayed from the application of an operating potential to a power supply terminal comprising;

input and output terminals;
coupling means for continuously coupling said input terminal to said power supply terminal;
a source of clock pulses;
a first capacitor having a first capacitance value and a second capacitor having a second capacitance value substantially greater than said first capacitance value;
first switch means having first and second terminals defining the ends of a conduction path and a control terminal for controlling the conduction of said conduction path, said first terminal being coupled to said input terminal, said second terminal being coupled to said first capacitor, and said control terminal being coupled to said source of clock pulses and being responsive to a first level of said clock pulses for charging said first capacitor to a predetermined voltage level;
second switch means having first and second terminals defining the ends of a conduction path and a control terminal for controlling the conduction of said conduction path, said first terminal being coupled to said first capacitor, said second terminal being coupled to said second capacitor, and said control terminal being coupled to said source of clock pulses and being responsive to a second level of said clock pulses for transferring only a portion of the charge stored on said first capacitor to said second capacitor to thereby increase the voltage level developed across said capacitor by an incremental amount substantially less than said predetermined voltage level in response to each clock pulse;
and
threshold detector means having an input coupled to said second capacitor and an output coupled to said output terminal and being responsive to the voltage developed across said second capacitor for providing an output indication at said output terminal when the voltage developed across said second capacitor increases above a predetermined threshold level.

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Dependencies are inferred from the claim text.

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Abstract

A pulse counter type power-up circuit providing an output indication delayed from the application of an operating potential to a power supply terminal comprising;

input and output terminals;
coupling means for continuously coupling said input terminal to said power supply terminal;
a source of clock pulses;
a first capacitor having a first capacitance value and a second capacitor having a second capacitance value substantially greater than said first capacitance value;
first switch means having first and second terminals defining the ends of a conduction path and a control terminal for controlling the conduction of said conduction path, said first terminal being coupled to said input terminal, said second terminal being coupled to said first capacitor, and said control terminal being coupled to said source of clock pulses and being responsive to a first level of said clock pulses for charging said first capacitor to a predetermined voltage level;
second switch means having first and second terminals defining the ends of a conduction path and a control terminal for controlling the conduction of said conduction path, said first terminal being coupled to said first capacitor, said second terminal being coupled to said second capacitor, and said control terminal being coupled to said source of clock pulses and being responsive to a second level of said clock pulses for transferring only a portion of the charge stored on said first capacitor to said second capacitor to thereby increase the voltage level developed across said capacitor by an incremental amount substantially less than said predetermined voltage level in response to each clock pulse;
and
threshold detector means having an input coupled to said second capacitor and an output coupled to said output terminal and being responsive to the voltage developed across said second capacitor for providing an output indication at said output terminal when the voltage developed across said second capacitor increases above a predetermined threshold level.

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