High efficiency charge pump circuit for negative high voltage generation at 2 V supply voltage

A charge pump circuit has been developed for the generation of negative high voltage at supply voltage levels down to 2V. The generated high voltage is suitable for programming Flash EEPROM cells, that use Fowler-Nordheim tunneling. The key issue of the circuit design has been high efficiency and small chip area. The circuit consists of n-MOS transfer gates in a triple-well structure and is driven by a four phase clocking scheme. The power efficiency of a charge pump, designed for low power applications, is better than 25% at an output power of 100µW, including clock generation and voltage regulation.