APPARATUS AND METHOD FOR CHARGE PUMP SLEW RATE CONTROL
First Claim
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1. A system for providing an adaptive slew rate voltage signal to a memory cell, the system comprising:
- a charge pump coupled to a switch, the charge pump having a charge pump current, a charge pump load capacitance, and a charge pump voltage level, wherein the charge pump drives an output node having an output node voltage level at a first slew rate for a first voltage range;
a threshold voltage detection circuit coupled to a level shifter, a delay circuit, and the output node, wherein the threshold voltage detection circuit comprises a voltage divider circuit coupled to a comparator circuit;
a slew rate control circuit coupled to the delay circuit, the charge pump, and the output node; and
wherein the threshold voltage detection circuit generates a detection signal when the output node voltage level reaches a predetermined threshold voltage level, the detection signal communicated to the level shifter coupled to the switch to disable the charge pump and enable the slew rate control circuit to drive the output node voltage level at a second slew rate less than the first slew rate for a second voltage range.
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Abstract
An apparatus and method for improving memory cell reliability is disclosed. The slew rate is reduced in an applied voltage signal used to program a memory cell when Fowler-Nordheim (FN) tunneling injection is detected. The applied programming signal is provided by a charge pump that is preferably a regulated charge pump. The charge pump is selectively controlled by a slew rate control circuit when FN tunneling injection is detected by a voltage level detection circuit at a predetermined threshold voltage level.
39 Citations
29 Claims
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1. A system for providing an adaptive slew rate voltage signal to a memory cell, the system comprising:
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a charge pump coupled to a switch, the charge pump having a charge pump current, a charge pump load capacitance, and a charge pump voltage level, wherein the charge pump drives an output node having an output node voltage level at a first slew rate for a first voltage range; a threshold voltage detection circuit coupled to a level shifter, a delay circuit, and the output node, wherein the threshold voltage detection circuit comprises a voltage divider circuit coupled to a comparator circuit; a slew rate control circuit coupled to the delay circuit, the charge pump, and the output node; and wherein the threshold voltage detection circuit generates a detection signal when the output node voltage level reaches a predetermined threshold voltage level, the detection signal communicated to the level shifter coupled to the switch to disable the charge pump and enable the slew rate control circuit to drive the output node voltage level at a second slew rate less than the first slew rate for a second voltage range. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method for providing an adaptive slew rate voltage signal to a memory cell, the method comprising:
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driving an output node having an output node voltage level at a first slew rate for a first voltage range; detecting when the output node voltage level reaches a predetermined threshold voltage level; delaying driving of the output node voltage level for a predetermined delay period; and driving the output node voltage level at a second slew rate less than the first slew rate for a second voltage range subsequent to the predetermined delay period. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26)
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27. A machine readable storage medium having a stored set of instructions executable by a machine for providing an adaptive slew rate voltage signal to a memory cell, the instructions comprising:
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instructions to provide an output node voltage level at a first slew rate for a first voltage range, wherein the first voltage range is between a supply voltage level to a predetermined threshold voltage level; instructions to detect when the output node voltage level reaches the predetermined threshold voltage level; and instructions to provide the output node voltage level at a second slew rate less than the first slew rate for a second voltage range subsequent to a predetermined delay period, wherein the second voltage range is between the predetermined threshold voltage level to a high voltage level. - View Dependent Claims (28, 29)
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Specification