Method and apparatus for regulated low voltage charge pump
First Claim
Patent Images
1. A low voltage charge pump comprising:
- start-up clock circuit that produces a clock signal having a first clock phase and a second clock phase, and the start-up clock circuit operates from a supply voltage having a voltage difference of less than 2.6 volts between a voltage source and a common reference, wherein during a startup period the clock signal is produced without the presence of an external clock;
an output capacitor having a first terminal coupled to a reference voltage terminal, and a second terminal for providing an output voltage;
capacitance charge circuit comprising;
a current limiting device operably coupled to receive the clock signal, a first charge signal, a current limiting input signal, and to provide a second charge signal, wherein the current limiting device controls a rate of change of the second charge signal based on the current limiting input signal and the first charge signal;
a charge circuit capacitor operably coupled to receive the second charge signal from the current limiting device, and to the second terminal of the output capacitor, wherein during the first clock phase the charge circuit capacitor is charged based on the second charge signal, and during the second clock phase the charge circuit capacitance is being discharged into the output capacitor to produce an output voltage; and
regulation circuit operably coupled to receive the output voltage, and to provide the first charge signal, wherein the regulation circuit controls a maximum value of the first charge signal such that the output voltage is regulated.
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Abstract
Generation of an output voltage (28) greater than that of a reference voltage (20) is accomplished using a self starting low voltage charge pump (10). A start-up clock circuit (12) comprising a ring oscillator (40) is used to generate a ting oscillator clock signal (63) which can be used allow the charge pump (10) to begin operation before an external clock signal (44) is available.
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Citations
13 Claims
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1. A low voltage charge pump comprising:
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start-up clock circuit that produces a clock signal having a first clock phase and a second clock phase, and the start-up clock circuit operates from a supply voltage having a voltage difference of less than 2.6 volts between a voltage source and a common reference, wherein during a startup period the clock signal is produced without the presence of an external clock; an output capacitor having a first terminal coupled to a reference voltage terminal, and a second terminal for providing an output voltage; capacitance charge circuit comprising; a current limiting device operably coupled to receive the clock signal, a first charge signal, a current limiting input signal, and to provide a second charge signal, wherein the current limiting device controls a rate of change of the second charge signal based on the current limiting input signal and the first charge signal; a charge circuit capacitor operably coupled to receive the second charge signal from the current limiting device, and to the second terminal of the output capacitor, wherein during the first clock phase the charge circuit capacitor is charged based on the second charge signal, and during the second clock phase the charge circuit capacitance is being discharged into the output capacitor to produce an output voltage; and regulation circuit operably coupled to receive the output voltage, and to provide the first charge signal, wherein the regulation circuit controls a maximum value of the first charge signal such that the output voltage is regulated. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 12)
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11. A method for stepping up a low voltage source, the method comprising the steps of:
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a) receiving the low voltage source having a voltage having a voltage difference of less than 2.6 volts between a voltage source and a common reference; b) generating a reference clock signal having a first clock phase and a second clock phase from the low voltage source, wherein the reference clock signal is generated without the assistance of an external clock; c) charging a storage capacitor at a first charge level during the first clock phase from the low voltage power source; d) transferring at least a portion of charge in the storage capacitor to an output capacitor during the second clock phase, for providing an output voltage; e) replacing the reference clock signal with an externally received clock signal when a trip voltage is reached; and f) regulating the output voltage to a desired voltage by controlling the first charge level.
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13. A low voltage charge pump comprising:
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a start-up clock circuit coupled to receive a supply voltage having a voltage difference of less than 2.6 volts between a voltage source and a common reference, a threshold control signal, and having a clock output for providing a variable clock signal having a first clock phase and a second clock phase, wherein the variable clock signal operates at a first frequency when the threshold control signal has a value below a threshold value, and at a second frequency when the threshold control signal has a value above a threshold value; an output capacitor having a first terminal coupled to a reference voltage terminal, and a second terminal for providing an output voltage; a capacitance charge circuit operably coupled to receive the clock signal, wherein, during the first clock phase, the capacitance charge circuit is being charged, and during the second clock phase, the capacitance charge circuit is being discharged into the output capacitor to produce an output voltage; and a regulation circuit operably coupled to receive the output voltage, and providing the first charge signal, wherein the regulation circuit controls a maximum value of the first charge signal such that the output voltage is regulated.
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Specification