Supply voltage monitor
AssigneeSilicon Labs CP, Inc.
InventorKenneth W. Fernald
Life of this patent
Estimating the term…
Abstract
A voltage monitor having a bandgap reference circuit driven by a voltage to be monitored. The bandgap reference circuit produces a voltage and a second voltage that each vary with the voltage to be monitored. The magnitudes of these voltages are compared by an open loop comparator to provide a high speed output state. The output of the voltage monitor can be used to monitor a supply voltage and produce a reset signal to a processor if the supply voltage falls to a magnitude below a specified threshold.
Claims18
A voltage monitor circuit, comprising:
- a bandgap circuit having a pair of pn junctions, said bandgap circuit driven by a voltage to be monitored;
- a first node associated with a first pn junction for providing a first voltage;
- a second node associated with a second pn junction that provides a second voltage;
- and
- a comparator circuit having a first input coupled to a voltage produced by said first node, and a second input coupled to a voltage produced by said second node.
A voltage monitor circuit, comprising:
- a first resistor having a first terminal and a second terminal;
- a pn junction device having a first terminal and a second terminal, the first terminal of said pn junction device connected in series with the second terminal of said first resistor to define a first junction;
- a second resistor having a first terminal and a second terminal, a voltage to be monitored being coupled to the first terminals of said first and second resistors;
- a third resistor having a first terminal and a second terminal, the first terminal of said third resistor connected to the second terminal of said second resistor to define a second node;
- a second pn junction device having a first terminal and a second terminal, the first terminal of said second pn junction device connected to the second terminal of said third resistor;
- the second terminals of said first and second pn junction devices connected to a common potential;
- and
- a comparator circuit having a first input coupled to the first node, and said comparator circuit having a second input coupled to the second node, and an output of said comparator circuit providing an output of said voltage monitor circuit.
A method of monitoring a voltage, comprising the steps of:
- applying a voltage to be monitored as a supply voltage to a bandgap reference circuit;
- generating by said bandgap circuit a first voltage and a second voltage that each vary with the voltage to be monitored;
- and
- comparing with a comparator circuit the first voltage with the second voltage, and providing an output indicating a condition of the voltage to be monitored.
Dependencies are inferred from the claim text.