Floating-gate reference circuit

• US 7,034,603 B2
• Filed: 05/27/2003
• Issued: 04/25/2006
• Est. Priority Date: 05/27/2003
• Status: Active Grant

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Anderson, David V., Hasler, Paul Edward, Brady, Philomena Cleopha, Kucic, Matthew Raymond, Serrano, Guillermo José, Lo, Haw-Jing, Pereira, Angelo W., Adil, Farhan
• Primary Examiner(s): ZWEIZIG, JEFFERY SHAWN
• Application Number:
  US10/446,087
• Publication Number:
  US 20040240278A1
• Time in Patent Office: 1,064 Days
• Field of Search: 327/530, 327/534, 327/535, 327/537, 327/538, 327/540, 327/541, 327/543
• US Class Current: 327/538
• CPC Class Codes: G11C 27/005 with non-volatile charge storage, e.g. on floating gate or MNOS
• CPC Class Codes: G11C 7/14 Dummy cell management; Sense reference voltage generators
• CPC Class Codes: H03M 1/1057 by trimming, i.e. by individually adjusting at least part of the quantisation value generators or stages to their nominal values
• CPC Class Codes: H03M 1/36 simultaneously only, i.e. parallel type
• CPC Class Codes: H03M 1/74 Simultaneous conversion
• CPC Class Codes: H03M 3/386 over the full range of the converter, e.g. for correcting differential non-linearity
• CPC Class Codes: H03M 3/45 with distributed feedforward inputs, i.e. with forward paths from the modulator input to more than one filter stage
• CPC Class Codes: H03M 3/454 with distributed feedback, i.e. with feedback paths from the quantiser output to more than one filter stage

Abstract

Systems and methods are discussed for using a floating-gate MOSFET as a programmable reference circuit. One example of the programmable reference circuit is a programmable voltage reference source, while a second example of a programmable reference circuit is a programmable reference current source. The programmable voltage reference source and/or the reference current source may be incorporated into several types of circuits, such as comparator circuits, current-mirror circuits, and converter circuits. Comparator circuits and current-mirror circuits are often incorporated into circuits such as converter circuits. Converter circuits include analog-to-digital converters and digital-to-analog converters.

Claims

1. A system comprising:

a floating-gate charge programmer;

a switch operative to provide a program-mode of operation and a run-mode of operation; and

a first floating-gate field effect transistor that is programmable by the floating-gate charge programmer to store a first floating-gate charge when the switch is operative in the program-mode of operation, and to produce, when the switch is operative in the run-mode of operation, at least one of a first reference voltage or a first reference current proportional to the first floating-gate charge;

wherein the floating-gate charge programmer is opertive to generate a switch control signal to control operation of the switch.

2. The system of claim 1, wherein the first floating-gate field effect transistor is a part of a voltage comparator circuit.

3. The system of claim 1, further comprising a voltage comparator, wherein the first reference voltage is provided to a first input of the voltage comparator, an analog input signal is provided to a second input of the voltage comparator, and wherein the voltage comparator produces an output signal that is a digital representation of the difference in amplitudes between the first reference voltage and the analog input signal.

4. The system of claim 3, further comprising an analog-to-digital converter, wherein the voltage comparator is one of a plurality of voltage comparators, and the first floating-gate field effect transistor is one of a plurality of floating-gate field effect transistors that are used to produce a plurality of reference voltages.

5. The system of claim 1, further comprising a digital-to-analog converter containing a second floating-gate field effect transistor that is programmable by the floating-gate charge programmer to store a second floating-gate charge when the switch is operative in the program-mode of operation, and to produce, when the switch is operative in the run-mode of operation, at least one of a second reference voltage or a second reference current proportional to the second floating-gate charge.

6. The system of claim 5, wherein the digital-to-analog converter comprises a summing amplifier that combines at least one of the first reference voltage or the first reference current when enabled by a first digital logic, with at least one of the second reference voltage or the second reference current when enabled by a second digital logic, to produce an analog signal that is representative of the digital logic combination of the first and second digital logic.

7. The system of claim 6, wherein the amplitude of the first reference voltage has a binary relationship to the amplitude of the second reference voltage.

8. The system of claim 6, wherein the amplitude of the first reference current has a binary relationship to the amplitude of the second reference current.

9. The system of claim 1, further comprising a second floating-gate field effect transistor that is connected to the first floating-gate field effect transistor to form a current-mirror circuit wherein the source-drain current of the second floating-gate field effect transistor is proportional to the source-drain current of the first floating-gate field effect transistor.

10. The system of claim 1, further comprising a second floating-gate field effect transistor that is connected to the first floating-gate field effect transistor to form a current-summing circuit wherein the output current of the current-summing circuit is proportional to the sum of the source-drain currents of the first and the second floating-gate field effect transistors.

11. The system of claim 1, wherein the floating-gate charge programmer further comprises at least one of a voltage measurement circuit to measure the first floating-gate charge or a current measurement circuit to measure a source-drain current of the first floating-gate field effect transistor.

12. A system comprising:

a flash analog-to-digital converter containing a plurality of voltage comparators;

a switch operative to provide a program-mode of operation and a run-mode of operation;

a first floating-gate field effect transistor connected to a first voltage comparator in the plurality of voltage comparators, the first floating-gate field effect transistor being programmable to store a first floating-gate charge when the switch is operative in the program-mode of operation, and to produce, when the switch is operative in the run-mode of operation, a first reference voltage output that is proportional to the first floating-gate charge;

a second floating-gate field effect transistor connected to a second voltage comparator in the plurality of voltage comparators, the second floating-gate field effect transistor being programmable to store a second floating-gate charge and produce a second reference voltage that is proportional to the second floating-gate charge; and

a third floating-gate field effect transistor connected to a third voltage comparator in the plurality of voltage comparators, the third floating-gate field effect transistor being programmable to store a third floating-gate charge and produce a third reference voltage output that is proportional to the third floating-gate charge,

wherein the first voltage reference output, the second voltage reference output, and the third voltage reference output provide a logarithmic change in voltage reference amplitudes for a flash analog-to-digital conversion in the flash analog-to-digital converter.

13. A method of providing a reference, the method comprising:

providing a floating-gate field effect transistor;

providing a switch;

setting the switch in a first position to program a charge into the floating-gate field effect transistor, wherein programming the charge into the floating-gate field effect transistor includes;

connecting a gate terminal of the floating-gate field effect transistor to a first input terminal of a voltage buffer;

connecting an input voltage signal to a second input terminal of the voltage buffer;

providing a feedback capacitor that capacitively couples an output voltage of the voltage buffer to the gate terminal of the floating-gate field effect transistor;

selectively providing one of a hot-electron charge injection process and a tunneling process to the floating-gate field effect transistor to adjust the amplitude of charge stored in the floating-gate field effect transistor to a desired amplitude; and

measuring the output voltage of the voltage buffer to determine the amplitude of charge stored in the floating-gate field effect transistor; and

setting the switch in a second position to use the floating-gate field effect transistor as at least one of a voltage reference or a current reference.

14. The method of claim 13, wherein upon programming the charge into the floating-gate field effect transistor, further configuring the floating-gate field effect transistor as a voltage reference by:

disconnecting a lead of the feedback capacitor that is connected to the output terminal of a voltage comparator; and

connecting the lead of the feedback capacitor to a ground potential.

15. A method of providing a reference, the method comprising:

providing a floating-gate field effect transistor;

connecting a drain terminal of the floating-gate field effect transistor to a first supply voltage;

connecting a source terminal of the floating-gate field effect transistor to an injection voltage source;

selectively providing one of a hot-electron charge injection process and a tunneling process to the floating-gate field effect transistor to adjust the amplitude of charge stored in the floating-gate field effect transistor to a desired amplitude;

disconnecting the source terminal of the floating-gate field effect transistor from the injection voltage source;

connecting the source terminal of the floating-gate field effect transistor to the first supply voltage; and

using the floating-gate field effect transistor as a reference voltage node.

16. A method of providing a reference, the method comprising:

providing a floating-gate field effect transistor;

connecting a drain terminal of the floating-gate field effect transistor to a first supply voltage;

connecting a source terminal of the floating-gate field effect transistor to an injection voltage source;

selectively providing one of a hot-electron charge injection process and a tunneling process to the floating-gate field effect transistor to adjust the amplitude of charge stored in the floating-gate field effect transistor to a desired amplitude;

disconnecting the source terminal of the floating-gate field effect transistor from the injection voltage source;

connecting the source terminal of the floating-gate field effect transistor to a second supply voltage; and

using the floating-gate field effect transistor as a reference current source.

17. A method of providing a reference, the method comprising:

providing a floating-gate field effect transistor;

connecting a source terminal of the floating-gate field effect transistor to a first supply voltage;

connecting a drain terminal of the floating-gate field effect transistor to an injection voltage source;

selectively providing one of a hot-electron charge injection process and a tunneling process to the floating-gate field effect transistor to adjust the amplitude of charge stored in the floating-gate field effect transistor to a desired amplitude;

disconnecting the drain terminal of the floating-gate field effect transistor from the injection voltage source;

connecting the drain terminal of the floating-gate field effect transistor to the first supply voltage; and

using the floating-gate field effect transistor as a reference voltage node.

18. A method of providing a reference, the method comprising:

providing a floating-gate field effect transistor;

connecting a source terminal of the floating-gate field effect transistor to a first supply voltage;

connecting a drain terminal of the floating-gate field effect transistor to an injection voltage source;

selectively providing one of a hot-electron charge injection process and a tunneling process to the floating-gate field effect transistor to adjust the amplitude of charge stored in the floating-gate field effect transistor to a desired amplitude;

disconnecting the drain terminal of the floating-gate field effect transistor from the injection voltage source;

connecting the drain terminal of the floating-gate field effect transistor to a second supply voltage; and

using the floating-gate field effect transistor as a reference current source.

19. A method of providing a reference, the method comprising:

setting a switch in a first position to program a charge into a floating-gate field effect transistor;

connecting a gate terminal of the floating-gate field effect transistor to a first input terminal of a voltage buffer;

connecting an input voltage signal to a second input terminal of the voltage buffer; and

providing a feedback capacitor that capacitively couples an output voltage of the voltage buffer to the gate terminal of the floating-gate field effect transistor.

20. The method of claim 19, further comprising:

selectively providing one of a hot-electron charge injection process and a tunneling process to the floating-gate field effect transistor to adjust the amplitude of charge stored in the floating-gate field effect transistor to a desired amplitude; and

measuring the output voltage of the voltage buffer to determine the amplitude of charge stored in the floating-gate field effect transistor.

21. The method of claim 20, further comprising:

setting the switch in a second position to use the floating-gate field effect transistor as at least one of a voltage reference or a current reference.

22. A system comprising:

a floating-gate charge programmer;

a switch operative to provide a program-mode of operation and a run-mode of operation;

a digital-to-analog converter including;

a first floating-gate field effect transistor that is programmable by the floating-gate charge programmer to store a first floating-gate charge when the switch is operative in the program-mode of operation, and to produce, when the switch is operative in the run-mode of operation, at least one of a first reference voltage or a first reference current proportional to the first floating-gate charge; and

a second floating-gate field effect transistor that is programmable by the floating-gate charge programmer to store a second floating-gate charge when the switch is operative in the program-mode of operation, and to produce, when the switch is operative in the run-mode of operation, at least one of a second reference voltage or a second reference current proportional to the second floating-gate charge.

23. The system of claim 22, wherein the digital-to-analog converter comprises a summing amplifier that combines at least one of the first reference voltage or the first reference current when enabled by a first digital logic, with at least one of the second reference voltage or the second reference current when enabled by a second digital logic, to produce an analog signal that is representative of the digital logic combination of the first and second digital logic.

24. The system of claim 23, wherein the amplitude of the first reference voltage has a binary relationship to the amplitude of the second reference voltage.

25. The system of claim 23, wherein the amplitude of the first reference current has a binary relationship to the amplitude of the second reference current.

26. A system comprising:

a floating-gate charge programmer;

a switch operative to provide a program-mode of operation and a run-mode of operation; and

a first floating-gate field effect transistor that is programmable by the floating-gate charge programmer to store a first floating-gate charge when the switch is operative in the program-mode of operation, and to produce, when the switch is operative in the run-mode of operation, at least one of a first reference voltage or a first reference current proportional to the first floating-gate charge; and

a second floating-gate field effect transistor that is connected to the first floating-gate field effect transistor to form a current-mirror circuit wherein the source-drain current of the second floating-gate field effect transistor is proportional to the source-drain current of the first floating-gate field effect transistor.

27. A system comprising:

a floating-gate charge programmer;

a switch operative to provide a program-mode of operation and a run-mode of operation;

a first floating-gate field effect transistor that is programmable by the floating-gate charge programmer to store a first floating-gate charge when the switch is operative in the program-mode of operation, and to produce, when the switch is operative in the run-mode of operation, at least one of a first reference voltage and a first reference current proportional to the first floating-gate charge; and

a second floating-gate field effect transistor that is connected to the first floating-gate field effect transistor to form a current-summing circuit wherein the output current of the current-summing circuit is proportional to the sum of the source-drain currents of the first and the second floating-gate field effect transistors.