Fixed-current method for programming large floating-gate arrays
The speed and accuracy of programming large floating gate arrays is limited by precision of current measurement and pulse generator. In this paper a novel floating gate programming method is proposed which alleviates the requirement of accurate measurement and facilitates fast programming. As opposed to conventional approaches this method programs fixed value of currents onto the floating gate transistor at variable control gate voltage. The technique is used in conjunction with a coarse programming method, that utilizes the positive feedback nature of pFET injection to improve the speed of programming. Measured results from an array of floating gate cells, fabricated in a 0.5 /spl mu/m CMOS process demonstrate the effectiveness of this method to program currents in the order of few picoamperes with approximately 8 bits of resolution.