Systems and methods for reading ferroelectric memories
View Patent ↗A system and method are provided for reading ferroelectric memories in a manner that does away with a conventional requirement for inclusion of a charge or sense amplifier associated with each ferroelectric memory cell. Simple circuits are employed for modulating an AC signal that is generated and input, including wirelessly, to the circuits where a capacitance of a ferroelectric capacitor acts as a filter. Depending upon whether the ferroelectric memory (capacitor) is charged or discharged, it will have a different capacitance, which will affect the impedance that the signal sees. An ability to remotely read that signal difference, as an indication of capacitance, rather than an indication of charge, is provided to expand the use of ferroelectric memories to a broader spectrum of applications including use in RFID tags.
1. A circuit for reading a ferroelectric memory cell, comprising:
a ferroelectric capacitor that stores a binary polarization state representing a single data bit in a ferroelectric memory;
an additional capacitor with a first electrode connected to a first electrode of the ferroelectric capacitor;
a resistor connected to the first electrode of the ferroelectric capacitor;
a capacitance of the ferroelectric capacitor being measured as an indication of the polarization state of the ferroelectric capacitor; and
an alternating current voltage source connected to the ferroelectric capacitor via the additional capacitor applies an alternating current voltage signal to the ferroelectric capacitor,
the capacitance of the ferroelectric capacitor being measured by referencing changes in the alternating current voltage signal.
2. The circuit of claim 1 , further comprising a first direct current voltage source connected to the ferroelectric capacitor via the resistor that applies a direct current voltage signal to the ferroelectric capacitor to alter the polarization state of the ferroelectric capacitor.
3. The circuit of claim 2 , further comprising a second direct current voltage source connected to a second electrode of the ferroelectric capacitor that applies a direct current voltage signal to the ferroelectric capacitor to alter the polarization state of the ferroelectric capacitor.
4. The circuit of claim 1 , the ferroelectric capacitor, the additional capacitor and the resistor being printed circuit components.
5. The circuit of claim 1 , the ferroelectric capacitor, the additional capacitor and the resistor being disposed on one or more flexible substrates.
6. A method of reading a ferroelectric memory, comprising:
applying an alternating current voltage signal across a ferroelectric capacitor;
measuring, with a processor, a capacitance of the ferroelectric capacitor by referencing changes in the alternating current voltage signal in at least one of a positive and negative polarization state for the ferroelectric capacitor;
outputting a result of the measuring to a user as an indication of a polarization state of the ferroelectric capacitor representing a single data bit in the ferroelectric memory; and
applying a direct current voltage signal to a ferroelectric capacitor to alter a polarization state of the ferroelectric capacitor,
the capacitance of the ferroelectric capacitor being measured with the processor as the polarization state of the ferroelectric capacitor is altered by the direct current voltage signal.
7. The method of claim 6 , the ferroelectric memory comprising a printed electronic circuit component.
8. The method of claim 6 , the ferroelectric memory being disposed on one or more flexible substrates.
9. The method of claim 6 , the applying the alternating current signal and the measuring the capacitance being done wirelessly.
10. The method of claim 9 , the wirelessly applying the alternating current voltage signal and measuring being accomplished using at least one of inductive coupling and capacitive coupling.
11. The method of claim 6 , the reading of the ferroelectric memory being non-destructive to the data stored in the ferroelectric memory before the reading.
12. The method of claim 6 , the ferroelectric memory comprising a plurality of ferroelectric capacitors and coupled respective transistors as individual memory cells, the method further comprising writing or reading the individual memory cells independently by selecting the individual memory cells through activation of the coupled respective transistors for the individual memory cells.
13. The method of claim 6 , further comprising applying one of more of differential or offset correction techniques to improve a signal to noise ratio in a measured alternating current signal.
14. A system that reads a ferroelectric memory, comprising:
a ferroelectric memory comprising a cell including a ferroelectric capacitor;
an alternating current voltage source that applies an alternating current voltage signal across the ferroelectric capacitor;
a measuring device that measures a capacitance of the ferroelectric capacitor by referencing changes in the alternating current voltage signal in at least one of a positive and negative polarization state; and
a direct current voltage source that applies a direct current voltage signal to the ferroelectric capacitor to alter a polarization state of the ferroelectric capacitor,
the capacitance of the ferroelectric capacitor being measured as the polarization state of the ferroelectric capacitor is altered by the direct current voltage signal.
15. The system of claim 14 , the ferroelectric memory comprising a printed electronic circuit component.
16. The system of claim 14 , a plurality of the components of the system being disposed on one or more flexible substrates.
17. The system of claim 14 , the alternating current voltage source wirelessly applying the alternating current voltage using at least one of inductive coupling and capacitive coupling.
18. The system of claim 14 , the ferroelectric memory comprising a plurality of ferroelectric capacitors and associated transistors as individual memory cells, the individual memory cells being independently written or read by selecting the individual memory cells through activation of the associated transistors for each of the individual memory cells.
19. A non-transitory computer-readable medium storing instructions which, when executed by a processor, cause the processor to execute the steps of a method of reading a ferroelectric memory, comprising:
applying an alternating current voltage signal across the ferroelectric capacitor;
measuring a capacitance of the ferroelectric capacitor by referencing changes in the alternating current voltage signal in at least one of a positive and negative polarization state for the ferroelectric capacitor;
outputting a result of the measuring to a user as an indication of a polarization state of the ferroelectric capacitor representing a single data bit in the ferroelectric memory; and
applying a direct current voltage signal to a ferroelectric capacitor to alter a polarization state of the ferroelectric capacitor,
the capacitance of the ferroelectric capacitor being measured as the polarization state of the ferroelectric capacitor is altered by the direct current voltage signal.
20. The non-transitory computer-readable medium of claim 19 , the applying the alternating current voltage signal and the measuring the capacitance being done wirelessly using at least one of inductive coupling and capacitive coupling.