Design and Analysis of Multi-Level Voltage Generator for NAND Flash Operations Using a reference voltage Controlled Charge Pump

Efficient and precise voltage control must be pro- vided to ensure the reliable operation of memory cells. This paper presents a circuit for the generation and control of high voltage, specifically targeted for NAND Flash memory applica- tions. NAND Flash memory is a form of non-volatile memory where data is stored in a matrix of memory cells consisting of floating-gate transistors. Its widespread adoption in embedded systems, solid-state drives, and portable storage is attributed to its high density and rapid access speed. NAND Flash operation needs precise voltage levels in various operating modes: high voltages are required for erase and programming operations, while moderate voltages are required for reading operations. To achieve this, a dual-phase clocking scheme is coordinated with a voltage reference divider and a feedback comparator to dynamically regulate the output based on the selected memory mode. A positive level shifter converts low-voltage control signals to high-voltage levels necessary for word-line and bit-line control of NAND arrays. The proposed charge pump, integrated with a configurable reference voltage generator and operating with a 20pF load, eliminates the need for multiple taps or stage-specific control signals. It generates target voltages of 19V for erase, 15V for program (write), and 5V for read operations. In the absence of regulation, it achieves up to 26V with an efficiency of 72% and a peak-to-peak ripple of 0 mV.