Methods and apparatus to implement temperature insensitive threshold detection for voltage supervisors

A voltage supervisor having a first threshold voltage output, the voltage supervisor including:

• a scaling circuit having a first input terminal and a first output terminal, the first input terminal configured to be coupled to a supply voltage, the scaling circuit configured to generate a first threshold voltage and a second threshold voltage;
• and
• a comparison circuit having a second input terminal, a third input terminal, and a second output terminal, the second input terminal configured to be coupled to the supply voltage, the third input terminal coupled to the first output terminal, the comparison circuit configured to toggle the second output terminal at the first threshold voltage and at the second threshold voltage;
• and
• wherein the first threshold voltage is greater than a bandgap voltage.

A method comprising:

• initiating a first switch and deactivating a second switch responsive to a comparator output state going high, the comparator output state connected to a control terminal of the first switch and a control terminal of the second switch;
• generating a first voltage ratio and a first voltage corresponding to the first voltage ratio across a first resistor responsive to the first switch initiating and the second switch deactivating;
• in response to a supply voltage equaling a first threshold voltage, the first threshold voltage greater than a bandgap voltage:
• generating a second voltage across a second resistor that is equal to or proportional to the first voltage across the first resistor;
• comparing the first voltage and the second voltage;
• toggling the comparator output state responsive to the comparison of the first voltage and the second voltage;
• and
• deactivating the first switch and initiating the second switch to generate a second voltage ratio and a second threshold voltage responsive to the toggling of the comparator output state.