Stage protection in multi-stage charge pumps
Apparatus, systems, and methods are disclosed, including a charge pump having a pumping function that includes multiple pump stages connected in series. Each pump stage includes a capacitor node coupled to a capacitive element, a low-voltage device including a dielectric layer having a threshold voltage, and an output node coupled to the capacitor node through the low-voltage device. The charge pump also includes a common discharge circuit coupled between a reference voltage and a common node. The charge pump also includes multiple high-voltage diodes, each coupled between the output node of a respective pump stage and the common node. The common discharge circuit includes a current source configured to supply a current to the output nodes when the pumping function of the charge pump is disabled.
1. A charge pump having a pumping function comprising:
multiple low-voltage pump stages connected in series, wherein each pump stage comprises:
a capacitor node coupled to a capacitive element;
a low-voltage switching device comprising a dielectric layer having a threshold voltage; and
an output node coupled to the capacitor node through the low-voltage switching device;
a common discharge circuit coupled between a reference voltage and a common node; and
multiple high-voltage diodes, each coupled between the output node of a respective pump stage and the common node,
wherein the common discharge circuit comprises a current, source configured to supply a current to the output nodes when the pumping function of the charge, pump is disabled.
2. The charge pump of claim 1 , wherein the current source controls a discharge speed of the charge pump.
3. The charge pump of claim 2 , wherein a current of the current source is based on a sum of charges of the multiple pump stages after the charge pump is disabled at steady state.
4. The charge pump of claim 1 , wherein each of the pump stages is discharged to 0 volts when the charge pump is disabled.
5. The charge pump of claim 1 , wherein each of the pump stages is discharged to a discharge voltage, wherein the discharge voltage is greater than 0 volts.
6. The charge pump of claim 5 , wherein the discharge voltage is less than the threshold voltage.
7. The charge pump of claim 1 , wherein the high-voltage diodes do not pass current to the current source when the charge pump is enabled.
8. The charge pump of claim 1 , wherein the threshold voltage of the low-voltage switching threshold is 4 volts or less.
9. The charge pump of claim 1 , comprising:
multiple diodes, each coupled between the capacitor node of a respective pump stage and the output node of the respective pump stage.
10. A method for operating a charge pump, the method comprising:
selectively enabling a pumping function of a charge pump comprising multiple low-voltage pump stages connected in series providing a high-voltage output under steady state operation, wherein each low-voltage pump stage includes:
a capacitor node coupled to a capacitive element;
a low-voltage switching device comprising a dielectric layer having a threshold voltage; and
an output node coupled to the capacitor node through the low-voltage switching device;
selectively disabling the pumping function of the charge pump; and
supplying a current to the capacitor nodes of two or more of the multiple pump stages using a common discharge circuit coupled between a reference voltage and a common node when the pumping function of the charge pump is disabled, the current configured to reduce charge from the two or more pump stages of the multiple pump stages through multiple high-voltage diodes, each coupled between the output node of a respective pump stage and the common node.
11. The method of claim 10 , wherein the current source controls a discharge speed of the charge pump.
12. The method of claim 11 , wherein a current of the current source is based on a sum of charges of the n pump stages after the charge pump is disabled at the steady state.
13. The method of claim 10 , wherein the pump stages are discharged to 0 volts when the charge pump is disabled.
14. The method of claim 10 , wherein the pump stages are discharged to a discharge voltage, wherein the discharge voltage is greater than 0 volts.
15. The method of claim 14 , wherein the discharge voltage is less than the threshold voltage.
16. A charge pump comprising:
multiple low-voltage pump stages connected in series comprising:
a first pump stage comprising:
a first input node;
a first capacitor node coupled to a first capacitive element;
a first low-voltage switching device comprising a dielectric layer having a low-voltage threshold; and
a first output node coupled to the first capacitor node through the first low-voltage switching device; and
a second pump stage, comprising:
a second input node;
a second capacitor node coupled to a second capacitive element;
a second low-voltage switching device comprising a dielectric layer having a low-voltage threshold; and
a second output node coupled to the second capacitor node through the second low-voltage switching device;
multiple passive devices comprising:
a first high-voltage diode comprising a dielectric layer having a high-voltage threshold higher than the low-voltage threshold, the first high-voltage diode coupled between the first output node of the first pump stage and a common node; and
a second high-voltage diode comprising a dielectric layer having a high-voltage threshold higher than the low-voltage threshold, the second high-voltage diode coupled between the second output node of the second pump stage and the common node; and
multiple diodes comprising:
a first diode coupled between the first capacitor mode of the first pump stage and the first output node of the first pump stage; and
a second diode coupled between the second capacitor node of the second pump stage and the second output node of the second pump stage; and
a common discharge circuit comprising a current source coupled between a reference voltage and the common node,
wherein the charge pump has an enabled state and a disabled state, wherein the multiple pump stages are configured to provide a pumping function in the enabled state, and wherein the common discharge circuit is configured to discharge the first and second pump stages through the first and second high-voltage diodes in the disabled state.
17. The charge pump of claim 16 , wherein the first output node of the first pump stage is coupled to the second input node of the second pump stage.
18. The charge pump of claim 16 , wherein the common discharge circuit is coupled to the first output node of the first pump stage through the first high-voltage diode and to the second output node of the second pump stage through the second high-voltage diode.
19. The charge pump of claim 18 , wherein the common discharge circuit is coupled to the second input node of the second pump stage through the first high-voltage diode.
20. The charge pump of claim 16 , wherein the multiple low-voltage pump stages connected in series comprise:
a third pump stage comprising:
a third input node;
a third capacitor node coupled to a third capacitive element;
a third low-voltage switching device comprising a dielectric layer having a low-voltage threshold; and
a third output node coupled to the third capacitor node through the third low-voltage switching device,
wherein the multiple high-voltage diodes comprise a third high-voltage diode comprising a dielectric layer having a high-voltage threshold higher than the low-voltage threshold, the third high-voltage diode coupled between the third output node of the third pump stage and the common node, and
wherein the common discharge circuit is configured to discharge the first, second, and third pump stages through the first, second, and third high-voltage diodes in the disabled state.