Clock generator circuit for a charge pump

A charge pump system formed on an integrated circuit connectable to receive a voltage level from an external power supply, including:

• a charge pump to generate an output voltage from an input voltage;
• and
• a clock generator circuit coupled to provide a clock output at whose frequency the charge pump operates, wherein the frequency of the clock output is a decreasing function of the voltage level of the external power supply, wherein the clock generator circuit comprises:
• one or more delay elements having the clock output, an on-circuit high voltage level, and the voltage level of the external power supply as inputs and having a delay that is an increasing function of the voltage level of the external power supply;
• and
• a latch circuit having as input the output of the one or more delay elements and as output the clock output,
• wherein the one or more delay elements further have as input a reference voltage, each delay element including:
• a node;
• a differential amplifier having a first input connected to the node, a second input connected to receive the reference voltage, and an output supplying output of the delay circuit;
• a first capacitor connected between the on-circuit high voltage level and the node;
• a first switch connected between the on-circuit high voltage level and the node;
• a second capacitor having a first plate connected to the node;
• a second switch connected between the node and ground;
• a third switch connected to the second plate of the second capacitor
• a current source connected between the second switch and the node,
• wherein, when the output of the of the clock generator circuit has a first value, the first switch is closed, the second switch is open, and the third switch connects the second plate of the second capacitor to the on-circuit high voltage level, and, when the output of the of the clock generator circuit has a second value, the first switch is open, the second switch is closed, and the third switch connects the second plate of the second capacitor to the voltage level of the external power supply.

A method of of reducing power consumption in a charge pump system formed on an integrated circuit connectable to power supply external to the integrated circuit, comprising:

• receiving at a clock circuit the voltage level from the power supply external to the integrated circuit, an on-circuit high supply voltage level, and a reference voltage;
• generating in the clock circuit a clock signal having a frequency that is a decreasing function of the voltage level of the external power supply;
• providing the clock signal from the clock circuit to a charge pump;
• and
• operating the charge pump at said frequency to generate an output voltage from an input voltage, wherein generating the clock signal comprises:
• receiving at a delay element the clock signal and the voltage level of the power supply external to the integrated circuit, the on-circuit high supply voltage level, and the reference voltage;
• generating from the power supply external to the integrated circuit, the on-circuit high supply voltage level, and the reference voltage a delay that is an increasing function of the voltage level of the external power supply as output of the delay element;
• receiving at a latch circuit the output of the delay element;
• and
• providing the clock signal as output of the latch circuit.