Low voltage, high current pump for flash memory

Abstract

A charge pump 1 for operation in an integrated circuit having a power source Vdd. The pump is made of a plurality of pump cells 10 connected together. Each pump cell includes an inverter 50 having a port 42 to receive a negative bias input, a port 44 to receive a positive bias input, a port 38 to receive a clock input, and a port 40 to output an output clock signal at the same frequency of the clock input, but phase shifted by a predetermined amount determined by the signal levels of the negative bias and said positive bias. Also included in each pump cell is a capacitor 26. A circuit 20, 22, 24, for coupling the output clock signal to one port of the capacitor is also provided, as is a pair of diodes 28, 30, connected serially together, one end of the pair being connected to the power source and the other end 48 of the pair providing the output signal of the pump cell, the common point of the pair being connected to the other port of the capacitor. The pump cells are connected together such that the inverters are connected together to form a ring oscillator and such that the output signals are connected in parallel. The pump provides a stable source of high current at a moderately boosted voltage, with very low ripple, and is suitable for use with non-volatile, programmable memories.