A temperature compensation word-line voltage generator for multi-level cell NAND Flash memories

A word-line voltage generator is proposed to compensate temperature variations in the threshold voltages of flash memory cells by mixing a first current with a negative temperature coefficient with a second current with zero temperature dependency whose current is adjustable per level per operation. The measured results showed that 1) the output voltage could be adjusted from 0.15V to 2.5V with a resolution of 10mV at 90C, and 2) the temperature coefficient could be adjusted from 0 to -5mV/K with a resolution of -0.04mV/K. Thus, a temperature variation in V_t of the memory cells can be reduced to ±10% with the generator circuit. The generator consumed 500μA and occupied 0.24mm².