Drain voltage pump circuit for nonvolatile memory device
First Claim
1. A drain voltage pump circuit comprising:
- a ring oscillator circuit that provides at least three overlapping clock signals, each having a voltage profile and frequency controlled by the ring oscillator;
a plurality of pump sections, each of which is configured to pump a drain voltage (VD) node in response to a respective one of the clock signals;
the ring oscillator circuit individually controlling the frequency and the voltage profile of the clock signals so that the voltage at the VD node is pumped during an initial pumping interval from a VCC level to a target VD level and maintained throughout a programming cycle within a preset ripple range of the target VD level.
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Accused Products
Abstract
A program drain voltage pump is provided that employs multiple pumping sections that are adaptively controlled to provide a pumped drain voltage (VD) that rises smoothly and rapidly to an optimum VD level for programming EPROM or flash memory cells and maintains VD at the optimum level with minimal ripple. The pumping sections are configured to pump a common VD node that is coupled to the drains of the EPROM or flash memory cells. Each pumping section is driven by a clock signal whose pulses are out of phase with the clock signals driving the other pumping sections. All of the clock signals have roughly the same frequency. Due to the staggered clocks, each pump is activated during a different respective time period, which smooths out VD. Additionally, to provide an even faster and smoother pumped VD than with multiphase clocking alone, an embedded controller is provided that adaptively adjusts the frequency and slew rate of the various clock pulses throughout the pumping operation, which alters the amount by which VD is raised for a given clock pulse.
132 Citations
18 Claims
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1. A drain voltage pump circuit comprising:
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a ring oscillator circuit that provides at least three overlapping clock signals, each having a voltage profile and frequency controlled by the ring oscillator; a plurality of pump sections, each of which is configured to pump a drain voltage (VD) node in response to a respective one of the clock signals;
the ring oscillator circuit individually controlling the frequency and the voltage profile of the clock signals so that the voltage at the VD node is pumped during an initial pumping interval from a VCC level to a target VD level and maintained throughout a programming cycle within a preset ripple range of the target VD level. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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Specification