HIGH VOLTAGE GENERATING CIRCUIT FOR VOLATILE SEMICONDUCTOR MEMORIES

摘要

A high voltage generating circuit which provides a constant V PP output without any threshold voltage drop and which does not suffer from latch-up problems is described. Thus a voltage boosting circuit which provides for a boosted voltage V PP at an output node, from a supply voltage V DD, includes a precharge transistor element responsive to a precharge clock signal for transferring the supply voltage V DD to a boost node for precharging the boost node to the full supply voltage V DD. The circuit further includes a capacitive element connected between the boost node and a pump node, the capacitive element pumping the boost node in response to a pump voltage sign al applied to the pump node; and a switching element connected between the boost node a nd the output node, for transferring charge from the capacitive element to the outp ut node to provide the boosted voltage V PP. In particular the precharge transistor element is an PMOS transistor. Furthermore in order to prevent latch-up of the PMOS device s, a switching circuit is provided to maintain the substrate at the highest volta ge in the circuit.