Non-integer multi-stage negative charge pump with low area and high efficiency

An integrated circuit, comprising:

• a circuit supporting substrate;
• an LDO voltage regulator, disposed on the circuit supporting substrate, for providing an LDO output voltage;
• and
• a negative charge pump circuit, disposed on the circuit supporting substrate, including
• an input terminal and an output terminal, the input terminal supplying a charge-pump reference voltage (VDDW) to the negative charge pump circuit and an LDO supply voltage to the LDO voltage regulator, and the output terminal providing a voltage output from the negative charge pump circuit;
• a multiplicity of stages electrically coupled together in a sequence, including a last plurality of stages at the end of the sequence, an output of a stage being coupled to an input of a directly subsequent stage in the multiplicity, and wherein an output of the last plurality of stages in the sequence is electrically coupled to the output terminal;
• each stage in the multiplicity, except the last plurality of stages, at its output adds negative VDDW to a voltage at its input, and the last plurality of stages at its output adds a negative fraction of VDDW to a negative voltage at its input, and each stage in the multiplicity, except the last plurality of stages, is driven by an oscillator clock;
• the last plurality of stages at the end of the sequence is driven by a modulated repeating cycle of the oscillator clock that varies between oscillating during a first time interval or not oscillating during a second time interval;
• and
• wherein the first time interval is at least 50% of a total of the first time interval plus the second time interval, a duration of the first time interval and a duration of the second time interval are defined by an output voltage signal from a comparator circuit based on a comparison of a reference voltage to a feedback voltage from an output of a voltage divider circuit dividing a voltage difference between the output voltage of the last plurality of stages and the LDO output voltage.

A method for using a charge pump circuit, the method comprising:

• providing a charge pump circuit comprising a plurality of stages electrically coupled together in a sequence, an output of a stage being coupled to an input of a subsequent stage in the sequence, and wherein an output of a last stage in the sequence is electrically coupled to an output of the charge pump circuit;
• adding, at an output of each stage, except the last stage in the sequence, a charge-pump reference voltage (VDDW) to a voltage at an input of each stage;
• adding, at an output of the last stage, a fraction of VDDW to a voltage at its input;
• driving clock inputs of each stage, except the last stage, by an oscillator clock tracking signal based on an oscillator clock;
• driving clock inputs of the last stage by a modulated repeating cycle of the oscillator clock that varies between oscillating during a first time interval or not oscillating during a second time interval;
• and
• wherein the first time interval is at least 50% of a total of the first time interval plus the second time interval, and a duration of the first time interval and a duration of the second time interval are defined by comparing a reference voltage to a feedback voltage which is an output voltage from a voltage divider circuit dividing a voltage difference between an output voltage of the last stage and an LDO output regulated voltage.