High voltage cascaded charge pump
AssigneeNational Semiconductor Corporation
InventorsRichard B. Merrill, Whu-ming Young
Life of this patent
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Abstract
A cascaded charge pump includes multiple stages each providing a (nominal) 3 volt increment. Thus a charge pump having an 18 volt range is provided using a CMOS process which normally then allows integration on a single integrated circuit chip of a complex digital logic function such as a UART (universal asynchronous receiver and transmitter) with a high voltage function such as an RS-232 interface, including integrated capacitors for the RS-232 interface charge pump.
Claims7
A cascaded charge pump circuit formed on a single semiconductor substrate, comprising:
- a plurality of N charge pumps, each charge pump i having a first and second input terminal and an output terminal;
- a voltage supply terminal;
- a voltage reference terminal;
- and a circuit output terminal;
- wherein the first input terminal of a first charge pump i=1 in the plurality of charge pumps is connected to the voltage supply terminal, and the second input terminal of the first charge pump is connected to the voltage reference terminal;
- and wherein for each successive charge pump i, where i=2 to N, in the plurality of charge pumps, the first input terminal is connected to the output terminal of the i-1 charge pump, and the second input terminal is connected to the first input terminal of the i-1 charge pump;
- and wherein the output terminal of the charge pump i=N is connected to the circuit output terminal;
- and
- each charge pump is electrically isolated on the semiconductor substrate from the other charge pumps.
A method of generating a particular voltage level greater than a supply voltage level, comprising the steps of:
- providing a cascaded set of charge pumps, all elements of which are formed on a single integrated circuit chip;
- using the supply voltage level to generate an intermediate voltage higher than the supply voltage level by a predetermined amount using the cascaded charge pumps;
- and
- increasing the intermediate voltage by the predetermined amount n times, n being greater than one thereby generating a plurality of intermediate voltages;
- and
- wherein each charge pump is electrically isolated on the semiconductor substrate from the other charge pumps.
Dependencies are inferred from the claim text.