Low current power detection circuit providing window comparator functionality
View Patent ↗A power detection system is disclosed that includes a detector circuit and a comparator circuit. The detector circuit includes a first transistor, a second transistor that is not identical to the first transistor, and a third transistor that is substantially identical to the first transistor. Each of the transistors is commonly coupled to a current source and is coupled to a differential input voltage. The comparator circuit is for providing an output that is representative of whether the input voltage is above or below a threshold voltage responsive to a difference between the first transistor and the second transistor.
1. A power detection system comprising:
a detector circuit that includes a first transistor, a second transistor that is not identical to the first transistor, and a third transistor that is substantially identical to the first transistor, each of said transistors being commonly coupled to a current source and being coupled at a gate thereof to a differential input voltage; and
a comparator circuit for providing an output that is representative of whether the input voltage is above or below a threshold voltage responsive to a difference between the first transistor and the second transistor.
2. The power detection system as claimed in claim 1 , wherein said second transistor has a width that is different than a width of the first transistor.
3. The power detection system as claimed in claim 1 , wherein said first, second and third transistors are N-channel metal-oxide-semiconductor-field-effect-transistors.
4. The power detection system as claimed in claim 1 , wherein the comparator circuit includes a current mirror circuit for providing a replica current of a current through second transistor.
5. The power detection system as claimed in claim 1 , wherein the comparator circuit includes an integrating amplifier for providing an output signal.
6. The power detection system as claimed in claim 1 , wherein the current source is provided by a bias circuit that is controlled by a bias current.
7. The power detection system as claimed in claim 1 , wherein said power detection system is coupled to further comparator circuits in series.
8. The power detection system as claimed in claim 7 , wherein said further comparator circuits are coupled together via a voltage divider network.
9. The power detection system as claimed in claim 1 , wherein said comparator circuit is coupled to further comparator circuits in parallel.
10. The power detection system as claimed in claim 9 , wherein said further comparator circuits have current sources that provide different currents.
11. The power detection system as claimed in claim 9 , wherein said further comparator circuits have sets of three transistors that have different characteristics than characteristics of the first transistor, second transistor, and third transistors.
12. A power detection system comprising:
a first detector circuit that includes a first transistor, a second transistor that is not identical to the first transistor, and a third transistor that is substantially identical to the first transistor, each of said first, second and third transistors being commonly coupled to a first current source and being coupled to a first differential input voltage;
a second detector circuit that includes a fourth transistor, a fifth transistor that is not identical to the fourth transistor, and a sixth transistor that is substantially identical to the fourth transistor, each of said fourth, fifth and sixth transistors being commonly coupled to a second current source and being coupled to a second differential input voltage; and
a comparator circuit for providing an output that is representative of whether the first input voltage is above or below a first threshold voltage responsive to a difference between the first and second transistors, and that is representative of whether the first input voltage is above or below a second threshold voltage responsive to a difference between the fourth and fifth transistors.
13. The power detection system as claimed in claim 12 , wherein said second transistor has a width that is different than a width of the first transistor, and the fifth transistor has a width that is different than a width of the fourth transistor.
14. The power detection system as claimed in claim 12 , wherein a first ratio of a width of the second transistor minus a width of the first transistor minus a width of the third transistor to a product of the width of the first transistor multiplied by the width of the second transistor is different than a second ratio of a width of the fifth transistor minus a width of the fourth transistor minus a width of the sixth transistor to a product of the width of the fourth transistor multiplied by the width of the fifth transistor.
15. The power detection system as claimed in claim 12 , wherein said first and second current sources provide the same amount of current.
16. The power detection system as claimed in claim 12 , wherein said first current source provides a first current and the second current source provides a second current that is different than the first current.
17. The power detection system as claimed in claim 12 , wherein said first, second, third, fourth, fifth and sixth transistors are N-channel metal-oxide-semiconductor-field-effect-transistors.
18. The power detection system as claimed in claim 12 , wherein the first differential input voltage is the same as the second differential input voltage.
19. The power detection system as claimed in claim 12 , wherein the first differential input voltage is the different than the second differential input voltage.
20. A method of providing a voltage detector output, said method comprising the steps of:
receiving a first differential input voltage at a first comparator circuit that includes a first transistor, a second transistor that is not identical to the first transistor, and a third transistor that is substantially identical to the first transistor, each of said first, second and third transistors being commonly coupled to a first current source and being coupled to a first differential input voltage;
receiving a second differential input voltage at a second detector circuit that includes a fourth transistor, a fifth transistor that is not identical to the fourth transistor, and a sixth transistor that is substantially identical to the fourth transistor, each of said fourth, fifth and sixth transistors being commonly coupled to a second current source and being coupled to a second differential input voltage; and
providing an output that is representative of whether the input voltage is above or below a first threshold voltage responsive to a difference between the first and second transistors, and that is representative of whether the input voltage is above or below a second threshold voltage responsive to a difference between the fourth and fifth transistors.