Charge pump for conductive lines in programmable memory array

Abstract

A self-decoding charge pump for charging conductive lines (word lines or bit lines) of a semiconductor programmable memory array such as an EEPROM includes: oscillator output capacitive coupling circuitry connecting an oscillator output to a first control node corresponding to a selected conductive line, for capacitively coupling voltage pulses from the oscillator output to the first control node while the conductive line is selected; control selective charge transfer circuitry connecting a high voltage source to a second control node through the first control node, for selectively transferring charge increments from the high-voltage source to the second control node while the conductive line is selected; conductive line charging control circuitry connecting the high voltage source to the conductive line and responsive to the second control node, for selectively transferring charge from the high voltage source to the conductive line while the conductive line is selected; and conductive line isolation circuitry connecting the conductive line to the second control node, for selectively charging the second control node from the conductive line while the conductive line is selected, and for preventing a charging of the conductive line from the second control node. The conductive line isolation device allows decoupling the pumping efficiency of the charge pump from the capacitance of the conductive line to be charged. The efficiency of the pump depends on the capacitance of the second control node (a primary pump output), rather than the capacitance of the conductive line itself (a secondary pump output). Since the second control node can have a much lower capacitance than the conductive line, the described charge pumps allow substantially improved pumping efficiencies.