Current mode charge pumps
AssigneesMaxim Integrated Products, Inc., Gain Technology.Corporation
InventorRobert St. Pierre
Life of this patent
Estimating the term…
Abstract
Current mode charge pumps having improved power consumption characteristics and reduced peak current requirements. The current mode charge pumps utilize a differential transistor pair with a current source providing the tail current for the differential pair. The differential pair alternately steers the current of the current source through first and second fly capacitors, with additional circuitry coupling the opposite fly capacitor, previously charged, to the output of the charge pump. Selection of the tail current provides for matching of circuit performance with the required charge pump output voltage, the load current to be provided thereby and the start time requirements.
Claims18
A charge pump comprising:
- first and second power supply lines;
- a current source coupled to the first power supply line;
- first and second fly capacitors;
- first and second transistors forming a differential pair, each of the first and second transistors being coupled to the current source and a respective one of the first and second fly capacitors at first and second nodes respectively, the first and second transistors alternately steering the current source current to the first and second fly capacitors;
- first and second rectifying devices coupled to the first and second fly capacitors at third and fourth nodes, and to the second power supply line, respectively, the first and second rectifying devices allowing current flow in a direction to charge the fly capacitors by a voltage difference between the first and second power supply lines and blocking current flow in the opposite direction;
- third and fourth rectifying devices coupling the third and fourth nodes to a charge pump output line, respectively, the third and fourth rectifying devices allowing current flow in a direction to discharge the fly capacitors by a voltage difference between the second power supply line and the charge pump output line and blocking current flow in the opposite direction;
- and,
- third and fourth transistors coupled between the first and second nodes and the second power supply line, the third and fourth transistors coupling the first and second nodes to the second power supply line when the second and first transistors couple the current source to the second and first fly capacitors, respectively.
In a charge pump wherein first and second fly capacitors are alternatively coupled to first and second voltages, an improvement comprising:
- a current source coupled to the first voltage;
- first and second transistors forming a differential pair, each transistor of the differential pair being coupled between the current source and a respective one of the fly capacitors, wherein the first and second transistors are MOS devices of a first conductivity type;
- and
- third and fourth transistors of a second conductivity type, each transistor being controlled by a respective transistor gate, first and second current sources and first and second coupling capacitors, the gates of the first and third transistors being coupled together, and coupled to the second voltage through the first current source, the gates of the second and fourth transistors being coupled together, and coupled to the second voltage through the second current source, wherein during a first phase of a clock signal driving said gates of said first and third transistors, the first transistor is turned on to couple said current source to respective fly capacitor to charge it, and during a second phase of said clock signal, the first current source turns on said third transistor to couple said first voltage to said respective fly capacitor to maintain an output voltage above said first voltage, and wherein during said second phase of said clock signal driving said gates of said second and fourth transistors, the second transistor is turned on to couple said current source to respective fly capacitor to charge it, and during said first phase of said clock signal, the second current source turns on said third transistor to couple said second voltage to said respective fly capacitor to maintain said output voltage above said second voltage.
A charge pump, comprising:
- a current source;
- a first capacitor;
- a second capacitor;
- a first switching mechanism to alternately couple said current source to said first and second capacitors to cause their respective charging;
- and
- a second switching mechanism to alternately couple said charged first and second capacitors to an output capacitor to produce an output voltage.
Dependencies are inferred from the claim text.