Methods and apparatus for temperature insensitive voltage supervisors

An apparatus comprising:

• a proportional to absolute temperature (PTAT) generation circuit including an output;
• a first resistor having a first terminal and a second terminal;
• a second resistor having a third terminal and a fourth terminal, the third terminal coupled to the second terminal at a first node;
• a first transistor including:
• a control terminal coupled to the fourth terminal of the second resistor at a second node;
• and
• a first current terminal coupled to the fourth terminal of the second resistor at the second node;
• a comparator including:
• a first input coupled to the output of the PTAT generation circuit at a third node;
• and
• a second input coupled to the second terminal and third terminal at the first node;
• a third resistor having a fifth terminal coupled to the third terminal and the second input at a fourth node;
• and
• wherein the PTAT generation circuit further includes:
• a current mirror having a first output current and a second output current;
• a fourth resistor having a sixth terminal and a seventh terminal, the sixth terminal coupled to the first output current at a fifth node;
• a second transistor including:
• a second control terminal coupled to the sixth terminal and the first output current at the fifth node;
• and
• a second current terminal coupled to the seventh terminal at a sixth node;
• a third transistor including:
• a third control terminal coupled to the second current terminal and the seventh terminal at the sixth node;
• a third current terminal coupled to the second output current at a seventh node;
• a fourth transistor including:
• a fourth control terminal coupled to the sixth terminal and the first output current at the fifth node;
• a fourth current terminal;
• and
• a fifth resistor having an eighth terminal and a ninth terminal, the ninth terminal coupled to the fourth current terminal at the third node.

A system comprising:

• a voltage supervisor including:
• a detection circuit configured to be coupled to a supply voltage, the detection circuit including:
• a proportional to absolute temperature (PTAT) generation circuit including:
• a first transistor having a first control terminal and a first current path coupled between a supply threshold voltage and ground;
• a second transistor having a second control terminal coupled to the first current path and a second current path coupled between the supply threshold voltage and ground;
• a third transistor having a third control terminal coupled to the first control terminal and a third current path coupled between the supply threshold voltage and ground;
• and
• a current mirror coupled between the first and second transistor and the supply threshold voltage;
• a comparator coupled to the PTAT generation circuit and having an output that is configured to toggle at a threshold voltage;
• and
• a circuit block including a circuit block input terminal coupled to the output terminal, the circuit block to operate at the threshold voltage, wherein the threshold voltage is less than a bandgap voltage.

A system comprising:

• a voltage supervisor including:
• a detection circuit configured to be coupled to a supply voltage, the detection circuit including:
• a proportional to absolute temperature (PTAT) generation circuit having an input terminal that is configured to be coupled to a supply voltage generator, the PTAT generation circuit further includes:
• a current mirror having a first output current terminal and a second output current terminal;
• a first resistor having a first terminal and a second terminal, the first terminal coupled to the first output current terminal at a first node;
• a first transistor including:
• a first base terminal coupled to the first terminal of the first resistor and the first output current terminal of the current mirror at the first node;
• and
• a first current terminal coupled to the second terminal of the first resistor at a second node;
• a second transistor including:
• a second base terminal coupled to the first current terminal of the first transistor and the second terminal of the first resistor at the second node;
• and
• a second current terminal coupled to the second output current terminal of the current mirror at a third node;
• a third transistor including:
• a third base terminal coupled to the first terminal of the first resistor and the first output current terminal of the current mirror at the first node;
• a third current terminal;
• and
• a second resistor having a third terminal and a fourth terminal, the third terminal coupled to the third current terminal of the third transistor at the third node;
• and
• a comparator having an output terminal that is configured to toggle at a threshold voltage;
• and
• a circuit block including a circuit block input terminal coupled to the output terminal, the circuit block to operate at the threshold voltage, wherein the threshold voltage less than a bandgap voltage.