Constant high voltage generator (CONSTANT HIGH VOLTAGE GENERATOR)

摘要

The high voltage generator circuit generates a high voltage used in the operation of the electrically erasable programmable read only memory. The circuit is described for on-chip MOS implementation. The charge pump, which is comprised of a plurality of stages, is driven by a plurality of phase clock signals operating from a 4-bit clock signal generator having a frequency determined by the input current. A comparator with an output current associated with a differential input indicates a truncated response where the output current is zero for a zero differential input and a maximum output current if the noninverting input potential substantially exceeds the inverting input potential. The noninverting input is connected to the reference potential and the inverting input is connected to receive a controlled portion of the high voltage generated by the charge pump. At startup, the fixed pressure is zero and the comparator applies a maximum current to the clock generator, which operates at the maximum frequency and minimizes the startup time. After startup, the clock frequency is proportional to the current drawn from the high voltage generator circuit.