Publication Date

5-2010

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Electrical Engineering

Department

Electrical and Computer Engineering

Supervisory Committee Chair

R. Jacob Baker, Ph.D.

Supervisory Committee Member

Kristy A. Campbell, Ph.D.

Supervisory Committee Member

Wan Kuang, Ph.D.

Abstract

Modern memory semiconductors require different internal voltages to accomplish the myriad of tasks that are required for operation. These internal voltages are multiples of the external voltage that is applied to the part. This multiple can be greater than one, as is the case with voltage pumps, less than one, as in the case of regulated supplies, and negative, as in the case of negative charge pumps. All of these potentials require control and regulation to ensure proper operation of the die. The control of the supply ensures that the required potentials are available when the die needs it. The regulation portion of the equation ensures that the desired potential is sufficient to meet the circuit needs and can react to changes in the circuit using the potential. This research explores the use of a Delta-Sigma Modulation-based circuit to control and regulate the operation of a voltage-generation circuit as well as introduce the ability to dynamically program the output voltage. What is presented in this thesis is the use of Delta-Sigma Modulation to sense, generate, and control the pumped wordline potentials necessary in a modern NAND memory device. These voltages generally consist of a read, erase, pass, and program potentials. The topology was chosen for voltage stability, superior response time when measured at the highest potential, and the ability to program the desired output potential depending on the circuit operation being performed. The proposed circuit was designed and fabricated using AMI’s 500 nm process through the MOSIS service (www.mosis.com). The chip performance has been evaluated and compared to the simulation results to verify accurate voltage generation over a wide input voltage and output response to changes in the input voltage. The control voltage was varied from 0.6 volts to 2.0 volts and the output voltages were measured to be 5.76 volts and 20.03 volts, respectively. The linearity of the output response was measured to average within 100 millivolts of the ideal. The response time of the DSM was also measured with good correlation to the simulation values.

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