Charge pump with charge feedback and method of operation
A charge pump charges a first capacitor to a predetermined input voltage using a first switch. The first switch is coupled to a first terminal of the first capacitor for coupling the first terminal to an input terminal that receives the predetermined input voltage. A second switch couples a second terminal of the first capacitor to a reference voltage terminal. Charge is sequentially transferred from the first capacitor to an output capacitance by using the first switch. A portion of charge is sequentially removed from the output capacitance to the input terminal using a third switch and a second capacitor. Configuration logic provides control signals to make one or more of a plurality of charge transfer capacitors switch the same as said first capacitor switches.
1. A charge pump, comprising:
a first capacitor having a first terminal and a second terminal;
a first switch coupled to the first terminal of the first capacitor for coupling the first terminal to either an input terminal for receiving an input voltage or to an output node;
a second switch coupled to the second terminal of the first capacitor for coupling the second terminal to either a reference voltage terminal or to the input terminal;
an output capacitance having a first terminal coupled to the second terminal of the first switch and having a second terminal coupled to the reference voltage terminal, the output capacitance receiving charge from the input terminal and the first capacitor;
a second capacitor having a first terminal and a second terminal, the second terminal being coupled to the reference voltage terminal; and
a third switch coupled to the first terminal of the second capacitor for selectively coupling the first terminal of the second capacitor to either the first terminal of the output capacitance or the input terminal, the second capacitor selectively removing charge from the output capacitance using the third switch and coupling said charge to the input terminal as feedback.
2. The charge pump of claim 1 further comprising:
a fourth switch coupled to the second terminal of the second capacitor for selectively alternating coupling of the second terminal of the second capacitor between the reference voltage terminal and the input terminal.
3. The charge pump of claim 1 further comprising:
a third capacitor having a first terminal and a second terminal;
a fourth switch coupled to the first terminal of the third capacitor for coupling the first terminal to either the output node or to the input terminal for receiving the input voltage; and
a fifth switch coupled to the second terminal of the third capacitor for coupling the second terminal to either the reference voltage terminal or to the input terminal.
4. The charge pump of claim 1 further comprising:
a plurality of feedback charge transfer capacitors, each having a first terminal and a second terminal;
a first plurality of switches, each being coupled to the first terminal of a respective one of the plurality of feedback charge transfer capacitors for coupling the first terminal of the respective one of the plurality of feedback charge transfer capacitors to either the output node or to the input terminal for receiving the input voltage; and
a second plurality of switches, each being coupled to the second terminal of a respective one of the plurality of feedback charge transfer capacitors for coupling the second terminal of the respective one of the plurality of feedback charge transfer capacitors to either the input terminal for receiving the input voltage or to the reference voltage terminal.
5. The charge pump of claim 4 further comprising:
configuration logic coupled to a control terminal of each of the second plurality of switches, the configuration logic providing control signals to make one or more of the plurality of feedback charge transfer capacitors switch the same as the first capacitor switches.
6. The charge pump of claim 5 wherein the configuration register generates a plurality of successive differing configuration values which selectively make an output voltage at the output node increase a same amount in response to successively changing configuration values.
7. The charge pump of claim 4 wherein the configuration logic further comprises:
a configuration register for storing user provided selection signals to select a desired regulated output voltage value; and
a plurality of logic gates, each of the plurality of logic gates providing a predetermined one of a plurality of control signals.
8. The charge pump of claim 7 wherein each of the plurality of logic gates has a first input for receiving an oscillating clock signal, a second input for receiving a predetermined bit of one of the user provided selection signals, and an output for providing the predetermined one of the plurality of control signals.
9. A method comprising:
charging a first capacitor to a predetermined input voltage using a first switch coupled to a first terminal of the first capacitor for coupling the first terminal to an input terminal for receiving the predetermined input voltage and using a second switch for coupling a second terminal of the first capacitor to a reference voltage terminal; and
sequentially transferring charge from the first capacitor to an output capacitance by using the first switch and sequentially removing a portion of charge from the output capacitance to the input terminal using a third switch and a second capacitor.
10. The method of claim 9 further comprising:
selectively coupling a first plurality of capacitors between the output capacitance and the input terminal in response to a user provided control signal of the charge pump having one of a plurality of values to select an output voltage value by determining a number of capacitors of the first plurality of capacitors which sequentially remove charge from the output capacitance.
11. The method of claim 10 further comprising:
configuring a portion of the first plurality of capacitors to assist the first capacitor to sequentially transfer charge to the output capacitance.
12. The method of claim 10 further comprising:
storing the user provided control signal for selecting the output voltage value of the charge pump in a configuration register; and
coupling logic circuitry to the configuration register for generating a selection signal for selecting the output voltage value.
13. The method of claim 12 further comprising:
successively generating a plurality of successive differing configuration values which make the output voltage value increase a same amount in response to successively changing configuration values.
14. A charge pump comprising:
first capacitance means having a first terminal and a second terminal;
a first switching means coupled to the first terminal of the first capacitance means for coupling the first terminal to either an input terminal for receiving an input voltage or to an output node for providing an output voltage;
a second switching means coupled to the second terminal of the first capacitance means for coupling the second terminal to either a reference voltage terminal or to the input terminal, the second switching means coupling the second terminal of the first capacitance means to the reference voltage terminal when the first switching means couples the first terminal of the first capacitance means to the input terminal, the second switching means coupling the second terminal of the first capacitance means to the input terminal when the first switching means couples the first terminal of the first capacitance means to the output node;
an output capacitance means having a first terminal coupled to the second terminal of the first switching means and having a second terminal coupled to the reference voltage terminal, the output capacitance means receiving charge from the input terminal and the first capacitance means;
a second capacitance means having a first terminal and a second terminal, the second terminal being coupled to the reference voltage terminal; and
a third switching means coupled to the first terminal of the second capacitance means for selectively coupling the first terminal of the second capacitance means to either the first terminal of the output capacitance means or the input terminal, the second capacitance means selectively removing charge from the output capacitance means using the third switching means and coupling said charge to the input terminal by coupling the first terminal of the second capacitance means to the first terminal of the output capacitance means and coupling the second terminal of the second capacitance means to the reference voltage terminal when the first switching means is coupling the first terminal of the first capacitance means to the output node and the second switching means is coupling the second terminal of the first capacitance means to the input terminal.
15. The charge pump of claim 14 further comprising:
a fourth switching means coupled to the second terminal of the second capacitance means for selectively alternating coupling of the second terminal of the second capacitance means to between the reference voltage terminal and the input terminal.
16. The charge pump of claim 14 further comprising:
a third capacitance means having a first terminal and a second terminal;
a fourth switching means coupled to the first terminal of the third capacitance means for coupling the first terminal to either the output node or to the input terminal for receiving the input voltage; and
a fifth switching means coupled to the second terminal of the third capacitance means for coupling the second terminal to either the reference voltage terminal or to the input terminal.
17. The charge pump of claim 14 further comprising:
a plurality of feedback charge transfer capacitance means, each having a first terminal and a second terminal;
a first plurality of switching means, each being coupled to the first terminal of a respective one of the plurality of feedback charge transfer capacitance means for coupling the first terminal of the respective one of the plurality of feedback charge transfer capacitance means to either the output node or to the input terminal for receiving the input voltage; and
a second plurality of switching means, each being coupled to the second terminal of a respective one of the plurality of feedback charge transfer capacitance means for coupling the second terminal of the respective one of the plurality of feedback charge transfer capacitance means to either the input terminal for receiving the input voltage or to the reference voltage terminal.
18. The charge pump of claim 17 further comprising:
configuration logic means coupled to a control terminal of each of the second plurality of switching means, the configuration logic means providing control signals to make one or more of the plurality of charge transfer capacitance means switch at a same time as the first capacitance means switches.
19. The charge pump of claim 18 wherein the configuration logic means further comprise:
configuration register means for storing user provided selection signals to select a desired regulated output voltage value; and
a plurality of logic gates, each of the plurality of logic gates providing a predetermined one of a plurality of control signals.
20. The charge pump of claim 19 wherein each of the plurality of logic gates has a first input for receiving an oscillating clock signal, a second input for receiving a predetermined bit of one of the user provided selection signals, and an output for providing the predetermined one of the plurality of control signals.