1.8 V Low-Transient-Energy Adaptive Program-Voltage Generator Based on Boost Converter for 3D-Integrated NAND Flash SSD

In this paper we present an adaptive program-voltage generator for 3D-integrated solid state drives (SSDs) based on a boost converter. The converter consists of a spiral inductor, a high-voltage MOS circuit, and an adaptive-frequency and duty-cycle (AFD) controller. The spiral inductor requires an area of only 5 × 5 mm² in an interposer. The high-voltage MOS circuit employs a mature NAND flash process. The AFD controller, implemented in a conventional low-voltage MOS process, dynamically optimizes clock frequencies and duty cycles at different values of output voltage, V_OUT. The power consumption, rising time, and circuit area of the program-voltage generator are 88%, 73%, and 85% less than those of a program-voltage generator with a conventional charge pump, respectively. The total power consumption of each NAND flash memory is reduced by 68%. We also present the design methodology of the high-voltage MOS circuit of the boost converter with a conventional NAND flash process, in which charge-pump-based program-voltage generators are implemented.