Granted Patent B2

US 7,626,427 · App. 11/196,415 · Granted Dec 1, 2009

Abstract

Claims (38)

1. A voltage comparator for comparing a comparison voltage with a threshold, the voltage comparator comprising:

a first voltage-to-current converter for converting a reference voltage, which determines the threshold, into a reference current that depends on the reference voltage;

a second voltage-to-current converter for converting the comparison voltage into a comparison current that depends on the comparison voltage;

an output stage for outputting a digital output level, the digital output level being dependent on the reference current and the comparison current, the output stage being connected to a current summation node, wherein the comparison current and a threshold current are added, wherein the threshold current is dependent on the reference current, wherein at least one of the threshold current or the comparison current assumes a negative value in the summation; and

a transistor configured to limit the voltage applied between the current summation node and a ground connection of the output stage,

wherein the current summation node is configured to be connected via the transistor to the second voltage-to-current converter, the transistor having a higher breakdown voltage than the output stage.

2. The voltage comparator according to claim 1 , wherein the output stage is connected to a current summing node in which the comparison current and a threshold current, which depends on the reference current, are summed, and wherein one of the comparison current or the threshold current enters into the summation as a negative value.

3. The voltage comparator according to claim 2 , wherein the reference current is multiplied by a multiplication factor so that the threshold current entering into the summation in the current summing node depends on the multiplication factor and the reference current.

4. The voltage comparator according to claim 3 , wherein a reference current mirror, whose current mirror ratio can be adjusted or switched, is provided to multiply the reference current by the multiplication factor.

5. The voltage comparator according to claim 2 , wherein the digital output level is determined by a voltage at the current summing node, which voltage depends on the comparison current and the threshold current.

6. A voltage comparator for comparing a comparison voltage with a threshold, the voltage comparator comprising:

a first voltage-to-current converter for converting a reference voltage, which determines the threshold, into a reference current that depends on the reference voltage;

a second voltage-to-current converter for converting the comparison voltage into a comparison current that depends on the comparison voltage;

an output stage for outputting a digital output level, the digital output level being dependent on the reference current and the comparison current; and

a voltage limiter for limiting the voltage present between the current summing node and a ground connection of the output stage,

wherein the output stage is connected to a current summing node in which the comparison current and a threshold current, which depends on the reference current, are summed, and wherein one of the comparison current or the threshold current enters into the summation as a negative value.

7. The voltage comparator according to claim 6 , wherein the current summing node is connected through at least one first transistor to a current mirror that is connected to the first voltage-to-current converter, and wherein the first transistor, which functions as a voltage limiter, has a higher breakdown voltage rating than the output stage.

8. The voltage comparator according to claim 7 , wherein the gate or the base of the first transistor is connected to a supply voltage of the output stage.

9. The voltage comparator according to claim 6 , wherein the current summing node is connected to the first voltage-to-current converter through a second transistor, the second transistor being a voltage-limiter and has a higher breakdown voltage rating than the output stage.

10. The voltage comparator according to claim 9 , wherein a gate or a base of the second transistor is connected to a supply voltage of the output stage.

11. The voltage comparator according to claim 1 , wherein the first voltage-to-current converter and the second voltage-to-current converter are arranged on a semiconductor chip adjacent to one another or placed within one another.

12. The voltage comparator according to claim 1 , wherein the first voltage-to-current converter and the second voltage-to-current converter have the same components.

13. The voltage comparator according to claim 1 , wherein the first voltage-to-current converter has a current mirror with at least one resistor connected in series, and/or the second voltage-to-current converter has a current mirror with at least one resistor connected in series.

14. A voltage comparator for comparing a comparison voltage with a threshold, the voltage comparator comprising:

a first voltage-to-current converter for converting a reference voltage, which determines the threshold, into a reference current that depends on the reference voltage;

a second voltage-to-current converter for converting the comparison voltage into a comparison current that depends on the comparison voltage; and

an output stage for outputting a digital output level, the digital output level being dependent on the reference current and the comparison current,

wherein the output stage is connected to a current summing node in which the comparison current and a threshold current, which depends on the reference current, are summed, and wherein one of the comparison current or the threshold current enters into the summation as a negative value, and

wherein a cross current is generated that depends on the reference current, wherein the cross current enters into the summation at the current summing node once with a negative sign and once with a positive sign, in addition to the reference current and the comparison current.

15. The voltage comparator according to claim 2 , wherein the output stage has a Schmitt trigger whose output is connected to the current summing node.

16. The voltage comparator according to claim 1 , wherein components of the voltage comparator are integrated on a semiconductor chip, and wherein the reference voltage is connected to a connection of the semiconductor chip.

17. The voltage comparator according to claim 1 , wherein the comparison voltage is a differential voltage that is provided to inputs of the voltage comparator.

18. The voltage comparator according to claim 17 , wherein the second voltage-to-current converter converts a positive and a negative differential voltage, wherein the second voltage-to-current converter has a first current mirror associated with the positive differential voltage and a second current mirror associated with the negative differential voltage.

19. The voltage comparator according to claim 17 , wherein the second voltage-to-current converter has a breakdown voltage rating that is higher than the voltage values of a supply voltage of the output stage or a maximum reference voltage and is suited to a maximum common-mode input voltage that can be applied at two inputs.

20. The voltage comparator according to claim 1 , further comprising a switch for switching off a supply voltage of the output stage so that the voltage comparator is switched between a sleep mode and an operating mode.

21. The voltage comparator according to claim 1 , wherein the voltage comparator analyzes and/or monitors a voltage generated by a charge pump.

22. An analog to digital converter that uses a successive approximation method or counting method to convert a comparison voltage curve over time into digital output signals with a voltage comparator according to claim 1 .

23. The voltage comparator according to claim 1 , wherein the output of the comparator is compatible with the logic levels of multiple circuit families.

Assignments (11)