Charge pump systems and methods

• US 20070170979A1
• Filed: 11/27/2006
• Published: 07/26/2007
• Est. Priority Date: 11/25/2005
• Status: Abandoned Application

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Micheloni, Rino, Campardo, Giovanni
• Application Number:
  US11/605,193
• Publication Number:
  US 20070170979A1
• Time in Patent Office: Days
• US Class Current: 327/536
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps

Abstract

A charge pump circuit includes capacitors and a number of forcing circuits for forcing the voltages on various nodes of the charge pump. The forcing circuits ensure that voltage differences across components thereof are up-limited in absolute value by a predetermined maximum voltage equal to a multiple of the absolute value of the difference between developed forcing voltages and lower than an absolute value of a charge pump voltage. The first and second forcing circuits ensure that the voltage differences across components in the forcing circuits are not higher than the predetermined maximum voltage when at least one among the voltages changes to a voltage higher in absolute value than said predetermined maximum voltage.

Claims

1. A charge pump circuit comprising at least one pump stage, said pump stage including:

a capacitor having a first plate and a second plate;

a first circuital node connected to the first plate, a voltage of the first circuital node being forced to a first forced voltage during a forcing phase of the charge pump operation;

a second circuital node connected to the second plate, a voltage of the second circuital node being forced to a second forced voltage during the forcing phase, the voltages of the first and the second circuital nodes being free of changing with respect to the first and to the second forced voltages, respectively, except during said forcing phase,;

a first forcing circuit associated to the first circuital node, the first forcing circuit being activable for forcing the voltage of the first circuital node to the first forced voltage during the forcing phase; and

a second forcing circuit associated to the second circuital node, the second forcing circuit being activable for forcing the voltage of the second circuital node to the second forced voltage during the forcing phase,

wherein the first and second forcing circuits comprise each at least one electronic device having terminals,

wherein;

said at least one electronic device is designed to guarantee the capability of sustaining voltage differences across the terminals thereof that are up-limited in absolute value by a predetermined maximum voltage equal to a multiple of the absolute value of the difference between the first and the second forcing voltages and lower than an absolute value of a charge pump output voltage; and

the first and second forcing circuits include means for ensuring that the voltage difference applied across pair of terminals of said at least one electronic device is not higher than the predetermined maximum voltage when at least one among the voltages of the first and the second circuital nodes change to a voltage higher in absolute value than said predetermined maximum voltage.

2. The charge pump circuit of claim 1, wherein at least one among said first and second forcing circuits comprises:

a switch inserted between the respective circuital node and a forcing voltage supplier terminal, the switch including a control terminal, a first terminal connected to the respective circuital node and a second terminal connected to the forcing voltage supplier terminal;

a switch activation circuit connected to the control terminal of the switch, adapted to activate the switch during the forcing phase in such a way to transfer the first, respectively second forced voltage to the first, respectively second circuital node; and

a bootstrap circuit coupled to the respective circuital node and the control terminal of the switch, the bootstrap circuit being connected between the first, respectively second circuital node and the control terminal of the switch and being adapted to ensure that a voltage difference across the control, the first and the second terminals of the switch and between the switch control terminal and the switch activation circuit when the voltage of the first, respectively second circuital node changes with respect to the first, respectively second forced voltage is not higher in absolute value than the predetermined maximum voltage.

3. The charge pump of claim 2, wherein the bootstrap circuit of the first forcing circuit includes first coupling means for coupling the voltage of the first circuital node to the control terminal of the switch, and the bootstrap circuit of the second forcing circuit includes second coupling means for coupling the voltage of the second circuital node to the control terminal of the switch.

4. The charge pump of claim 3, wherein the first coupling means includes at least one first controlled voltage transfer mean having a control terminal adapted to be driven by voltages higher than the higher between the first and second forcing voltages or lower than the lower between the first and second reference forcing voltages for ensuring that a voltage difference between the control terminal of the at least one first controlled voltage transfer mean, the first circuital node, and the switch control terminal is not higher in absolute value than the predetermined maximum voltage.

5. The charge pump of claim 2, wherein both the first and the second forcing circuits comprise the switch, the switch activation circuit, and the bootstrap circuit.

6. The charge pump of claim 5, wherein the second coupling means include at least one second controlled voltage transfer mean having a control terminal adapted to be driven by voltages higher than the higher between the first and second forcing voltage for ensuring that a voltage difference between the control terminal of the at least one second controlled voltage transfer mean, the second circuital node, and the switch control terminal is not higher in absolute value than the predetermined maximum voltage.

7. The charge pump of claim 6, wherein the at least one among the first and second forcing circuits includes a voltage supplier circuit, coupled to the forcing voltage supplier terminal, capable to provide the first or, respectively, the second forced voltage for forcing the first, respectively second circuital node.

8. The charge pump of claim 7, wherein the voltage supplier circuit of the first forcing circuit is capable to interrupt the supply of the first forced voltage to the first circuital node during at least a phase different from the forcing phase;

and

the bootstrap circuit of the second forcing circuit is capable to deactivate the switch during at least a phase different from the forcing phase.

9. The chare pump of claim 2, wherein:

the first forcing circuit comprises the switch, the switch activation circuit, and the bootstrap circuit; and

the second forcing circuit is capable to interrupt the supply of the second forced voltage to the second circuital node during at least a phase different from the forcing phase.

10. The charge pump of claim 9, wherein the first forcing circuit includes a voltage supplier circuit coupled to the forcing voltage supplier terminal, capable to provide the first forced voltage for forcing the first circuital node, said voltage supplier circuit being capable to interrupt the supply of the first forced voltage to the first circuital node during at least a phase different from the forcing phase.

11. The charge pump of claim 1, wherein said at least one pump stage includes at least a first and a second pump stages cascade connected by means of switching means, the second circuital node of the first pump stage being connected to the first circuital node of the second boost stage by means of the switching means.

12. The charge pump of claim 1, further including:

an output node for providing the charge pump output voltage, the output node being a first or a second circuital node of a pump stage; and

a first regulating circuit connected to the forcing voltage supplier terminal adapted to set the charge pump output voltage to a desired regulated voltage by regulating the voltage of the forcing voltage supplier terminal.

13. The charge pump of claim 1, further including:

an output node for providing an output boosted voltage, the output node being a first or a second circuital node of a pump stage; and

a second regulating voltage connected between the forcing voltage supplier terminal and the output node adapted to regulate the charge pump output voltage by selectively interrupting the providing of the voltage of the forcing voltage supplier terminal basing on a comparison between the charge pump output voltage and a reference voltage.

14. The charge pump of claim 1, wherein the first and second forcing circuits includes only electronic devices designed to guarantee the capability of sustaining voltage differences across terminals thereof that are up-limited in absolute value by a predetermined maximum voltage equal to the absolute value of the difference between the first and the second forcing voltages and lower than a charge pump output voltage.

15. The charge pump of claim 1, wherein said multiple is equal to one.

16. The charge pump of claim 1, wherein:

said multiple includes a first multiple and a second multiple lower than the first multiple;

the predetermined maximum voltage includes a first predetermined maximum voltage equal to the first multiple of the absolute value of the difference between the first and the second forcing voltages and a second predetermined maximum voltage equal to the second multiple of the absolute value of the difference between the first and the second forcing voltages; and

the at least one electronic device is selected from the group consisting of a first electronic device and a second electronic device, the first electronic device being designed to guarantee the capability of sustaining voltage differences across terminals thereof that are up-limited in absolute value by the first predetermined maximum voltage and lower than a charge pump output voltage and the second electronic device being designed to guarantee the capability of sustaining voltage differences across terminals thereof that are up-limited in absolute value by the second predetermined maximum voltage and lower than a charge pump output voltage.

17. A method of operating a charge pump circuit comprising at least one charge pump stage including:

a capacitor having a first plate and a second plate;

a first circuital node connected to the first plate;

a second circuital node connected to the second plate;

a first forcing circuit associated with the first circuital nodes for forcing the voltage of the first circuital node exploiting at least one electronic device having terminals; and

a second forcing circuit associated with the second circuital nodes for forcing the voltage of the second circuital node exploiting at least one electronic device;

the method including the steps of;

forcing the voltage of the first circuital node to a first forced voltage during a forcing phase of the charge pump operation; and

forcing the voltage of the second circuital node to a second forcing voltage during the forcing phase,

wherein said steps of forcing the voltage include;

ensuring that the voltage difference applied across the terminals of said at least one electronic device is not higher than a predetermined maximum voltage equal to a multiple of the absolute value of the difference between the first and the second forcing voltages and lower than an absolute value of a charge pump output voltage when at least one among the voltages of the first and the second circuital nodes change to a voltage higher in absolute value than said predetermined maximum voltage.

18. A charge pump comprising at least one pump stage circuit and a forcing circuit coupled to each pump stage circuit, each pump stage circuit including a plurality of electronic components and the forcing circuit being adapted to receive first and second forcing voltages, the forcing circuit operable to control voltages applied to the electronic components of each pump stage circuit to develop a charge pump output voltage on an output of the pump stage circuit, the forcing circuit being further operable to limit voltages across the electronic components of each pump stage circuit to a maximum voltage having a magnitude equal to a multiple of the difference between the first and the second forcing voltages, the maximum voltage being less than a magnitude of the charge pump output voltage and the forcing circuit being further operable to limit voltages across each electronic component to the maximum voltage responsive to a voltage having a magnitude that is greater than the maximum voltage being applied to the component.

19. The charge pump of claim 18 wherein the first forcing voltage comprises a supply voltage the second forcing voltage comprises a ground reference voltage.

20. The charge pump of claim 18 wherein the electronic components comprise switches.

21. The charge pump of claim 20 wherein the switches comprise low-voltage MOS transistors.

22. The charge pump of claim 18 wherein the charge pump output voltage comprises a negative output voltage.

23. An integrated circuit, comprising:

electronic circuitry including a charge pump, the charge pump comprising at least one pump stage circuit and a forcing circuit coupled to each pump stage circuit, each pump stage circuit including a plurality of electronic components and the forcing circuit being adapted to receive first and second forcing voltages, the forcing circuit operable to control voltages applied to the electronic components of each pump stage circuit to develop a charge pump output voltage on an output of the pump stage circuit, the forcing circuit being further operable to limit voltages across the electronic components of each pump stage circuit to a maximum voltage having a magnitude equal to a multiple of the difference between the first and the second forcing voltages, the maximum voltage being less than a magnitude of the charge pump output voltage and the forcing circuit being further operable to limit voltages across each electronic component to the maximum voltage responsive to a voltage having a magnitude that is greater than the maximum voltage being applied to the component.

24. The integrated circuit of claim 23 wherein the electronic circuitry includes memory circuitry.

25. The integrated circuit of claim 24 wherein the memory circuitry includes non-volatile memory cells.

26. An electronic system, comprising:

electronic circuitry including an integrated circuit, the integrated circuit containing a charge pump comprising at least one pump stage circuit and a forcing circuit coupled to each pump stage circuit, each pump stage circuit including a plurality of electronic components and the forcing circuit being adapted to receive first and second forcing voltages, the forcing circuit operable to control voltages applied to the electronic components of each pump stage circuit to develop a charge pump output voltage on an output of the pump stage circuit, the forcing circuit being further operable to limit voltages across the electronic components of each pump stage circuit to a maximum voltage having a magnitude equal to a multiple of the difference between the first and the second forcing voltages, the maximum voltage being less than a magnitude of the charge pump output voltage and the forcing circuit being further operable to limit voltages across each electronic component to the maximum voltage responsive to a voltage having a magnitude that is greater than the maximum voltage being applied to the component.

27. The electronic system of claim 26 wherein the electronic circuitry comprises a computer system.

28. A method of controlling a charge pump circuit to provide a charge pump output voltage, the charge pump circuit including at least one pump stage circuit including a plurality of electronic components, the method comprising:

developing control voltages to control the operation of each pump stage circuit, the control voltages being derived from first and second forcing voltages;

limiting voltages across the electronic components of each pump stage circuit to a maximum voltage having a magnitude equal to a multiple of the difference between the first and the second forcing voltages, the maximum voltage being less than a magnitude of the charge pump output voltage; and

limiting voltages across each electronic component to the maximum when a voltage having a magnitude that is greater than the maximum voltage would be applied to the component.

29. The method of claim 28 wherein the charge pump output voltage comprises a negative output voltage.

30. The method of claim 28 wherein the first forcing voltage comprises a positive supply voltage and the second forcing voltage comprises a negative supply voltage.