High-voltage analog system for a mobile NAND flash

High-voltage analog circuits, including a novel high-voltage regulation scheme, are presented with emphasis on low supply voltage, low power consumption, low area overhead, and low noise, which are key design metrics for implementing NAND Flash memory in a mobile handset. Regulated high voltage generation at low supply voltage is achieved with optimized oscillator, high-voltage charge pump, and voltage regulator circuits. We developed a design methodology for a high-voltage charge pump to minimize silicon area, noise, and power consumption of the circuit without degrading the high-voltage output drive capability. Novel circuit techniques are proposed for low supply voltage operation. Both the oscillator and the regulator circuits achieve 1.5 V operation, while the regulator includes a ripple suppression circuit that is simple and robust. Through the paper, theoretical analysis of the proposed circuits is provided along with Spice simulations. A mobile NAND Flash device is realized with an advanced 63 nm technology to verify the operation of the proposed circuits. Extensive measurements show agreement with the results predicted by both analysis and simulation.