Charge pump having shunt diode for improved operating efficiency

• US 20070126494A1
• Filed: 12/06/2005
• Published: 06/07/2007
• Est. Priority Date: 12/06/2005
• Status: Abandoned Application

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Corporation (Western Digital Corporation)
• Inventors: Pan, Feng
• Application Number:
  US11/295,906
• Publication Number:
  US 20070126494A1
• Time in Patent Office: Days
• US Class Current: 327/538
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps

Abstract

The ramp up time of a change pump is decreased by providing shunt capacitors connecting nodes of the serially connected stages to the output terminal of the charge pump, thereby reducing the impedance of the charge pump and decreasing ramp up time.

Claims

1. A charge pump having improved charging efficiency comprising:

a) an input terminal for receiving an input voltage,

b) an output terminal for receiving a pumped voltage higher than the input voltage,

c) a plurality of charge stages serially connected between the input terminal and the output terminal, each stage having a node, a capacitor connected to the node for increasing node voltage when driven by a clock voltage, and a serial diode connecting the node to a succeeding node, and

d) at least one shunt diode connecting a node to the output terminal.

2. The charge pump as defined by claim 1 wherein a plurality of shunt diodes connect a plurality of nodes to the output terminal.

3. The charge pump as defined by claim 2 wherein each serial diode and each shunt diode comprises a diode connected NMOSFET.

4. The charge pump as defined by claim 3 wherein each shunt diode is smaller than each serial diode.

5. The charge pump as defined by claim 4 and further including a load capacitance connected to the output terminal, ramp up time for the output terminal voltage being a function of impedance of the plurality of charge stages and shunt diode times the load capacitance.

6. The charge pump as defined by claim 5 wherein each node is connected through a shunt diode to the output terminal.

7. The charge pump as defined by claim 1 wherein each node in connected through a shunt diode to the output terminal.

8. The charge pump as defined by claim 7 wherein each shunt diode is smaller than each serial diode.

9. The charge pump as defined by claim 8 wherein each serial diode and each shunt diode comprises a diode connected NMOSFET.

10. The charge pump as defined by claim 1 wherein each shunt diode is smaller than each serial diode.

11. The charge pump as defined by claim 10 and further including a load capacitance connected to the output terminal, the ramp up time for the output terminal voltage being a function of impedance of the plurality of charge stages time the load capacitance.

12. The charge pump as defined by claim 1 and further including a load capacitance connected to the output terminal, the ramp up time for the output terminal voltage being a function of impedance of the plurality of charge stages time the load capacitance.

13. A method of improving efficiency in a multi-stage charge pump, where each stage includes a node, a capacitor coupled to the node for increasing node voltage when driven by a clock voltage, and a serial diode coupling the node to a succeeding node, the method comprising the step of connecting at least one shunt diode between a node in the charge pump to an output terminal to facilitate charge transfer from the node to the output terminal, the shunt diode disconnecting the node as output voltage exceeds voltage on the node.

14. The method as defined by claim 13 wherein a plurality of shunt diodes are connected between a plurality of nodes and the output terminal.

15. The method as defined by claim 14 wherein all nodes are connected by shunt diodes to the output terminal.