Method to provide a higher reference voltage at a lower power supply in flash memory devices
First Claim
1. A fast voltage reference circuit, comprising:
- a bias supply configured to generate a bias supply voltage;
a variable divider circuit coupled to the bias supply by an active feedback path and configured to generate a variable reference voltage, the divider comprising;
an impedance;
a variable reference current circuit coupled to the impedance and configured to generate a current having a value based on a desired reference voltage and to conduct the current through the impedance, thereby generating the reference voltage associated therewith; and
a comparator circuit configured to compare the bias supply voltage to the reference voltage, and drive the bias supply and the variable divider circuit in response to the comparison, thereby quickly stabilizing the reference voltage.
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Accused Products
Abstract
A fast reference circuit having active feedback includes a bias supply circuit and a variable divider circuit connected by an active feedback path to the bias supply circuit, and a comparator circuit connected to the variable divider circuit, the bias supply circuit, and a reference node of the variable divider circuit. In one embodiment, a start-up circuit initially discharges a potential at the bias supply and comparator circuits, then initializes a reference voltage at the reference node at about zero volts to improve repeatability. In one embodiment, the variable voltage divider comprises an impendence that is trimmed based on a sheet resistance of a process used to fabricate the fast reference circuit, and further comprises a variable reference current circuit coupled to the impedance and configured to generate a current having a value based on a desired reference voltage and to conduct the current through the impedance, thereby generating the reference voltage associated therewith. The comparator circuit is configured to compare the bias supply voltage to the reference voltage, and drive the bias supply and the variable divider circuit in response to the comparison, thereby quickly stabilizing the reference voltage.
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Citations
29 Claims
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1. A fast voltage reference circuit, comprising:
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a bias supply configured to generate a bias supply voltage; a variable divider circuit coupled to the bias supply by an active feedback path and configured to generate a variable reference voltage, the divider comprising; an impedance; a variable reference current circuit coupled to the impedance and configured to generate a current having a value based on a desired reference voltage and to conduct the current through the impedance, thereby generating the reference voltage associated therewith; and a comparator circuit configured to compare the bias supply voltage to the reference voltage, and drive the bias supply and the variable divider circuit in response to the comparison, thereby quickly stabilizing the reference voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A fast voltage reference circuit, comprising:
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a bias supply configured to generate a bias supply voltage; a divider circuit coupled to the bias supply by an active feedback path from a feedback node of the divider circuit and configured to provide a reference voltage as a function of a voltage divider voltage ratio, comprising; a variable impedance configured to be selectively trimmed in response to a sheet resistance of a process employed to fabricate the fast voltage reference circuit; a variable reference current circuit configured to generate a current having a value based on a desired reference voltage at a reference node arranged between the variable impedance and the variable reference current; and a comparator circuit configured to compare the bias supply voltage to the reference voltage of the reference circuit, and operable to drive the bias supply and the variable divider circuit in response to the comparison, thereby quickly generating a stable reference voltage. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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21. A method of providing a fast and stable reference voltage, comprising:
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providing an impedance for a variable divider circuit; selecting a variable current reference for the variable divider circuit based on a desired reference voltage; translating the reference current through the impedance into the reference voltage; comparing the reference voltage to a bias supply voltage which varies as a function of feedback from a node of the variable divider circuit having a negative function of a supply voltage and substantially no function of temperature; and driving the differential voltage of the comparison into the variable divider circuit to rapidly stabilize the reference voltage substantially independent of variations in supply voltage and process variations. - View Dependent Claims (22, 23, 24, 25, 26)
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27. An electronic device, comprising:
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a user input configured to allow a user to input data; a user output configured to output data to a user; a central processing unit (CPU) operatively coupled to the user input and the user output and configured to receive and process the user input and to output the user output; and a memory operatively coupled to the CPU and configured to receive data from and send data to the CPU, the memory comprising a fast voltage reference circuit configured to supply a reference voltage (FVREF) to a wordline of the memory, the fast voltage reference circuit comprising a bias supply configured to generate a bias supply voltage, a variable divider circuit comprising an impedance and a variable reference current circuit, and a comparator circuit configured to compare the bias supply voltage to the reference voltage and drive the bias supply and the variable divider circuit in response to the comparison for outputting the reference voltage (FVREF) to the wordline as a function of variable reference current in the variable divider. - View Dependent Claims (28, 29)
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Specification