Device with neural network
A device with a neural network includes: a synaptic memory cell comprising a resistive memory element, which is disposed along an output line and which has either one of a first resistance value and a second resistance value, and configured to generate a column signal based on the resistive memory element and an input signal in response to the input signal being received through an input line; a reference memory cell comprising a reference memory element, which is disposed along a reference line and which has the second resistance value different from the first resistance value, and configured to generate a reference signal based on the reference memory element and the input signal; and an output circuit configured to generate an output signal for the output line from the column signal and the reference signal.
1. A device with a neural network, comprising:
a plurality of synaptic memory cells, disposed along a first output line, configured to generate a column signal based on resistive memory elements and input signals being received through a plurality of input lines, each of the plurality of synaptic memory cells comprising a resistive memory element having either one of a first resistance value or a second resistance value;
a plurality of reference memory cells, disposed along a reference line with sharing the plurality of input lines with the plurality of synaptic memory cells respectively, configured to generate a reference signal based on reference memory elements and the input signals, each of the plurality of reference memory cells comprising a reference memory element having the second resistance value different from the first resistance value; and
an output circuit configured to generate an output signal, for the first output line, indicating a difference between the column signal and the reference signal,
wherein the output circuit is configured to generate, as the output signal, a current corresponding to an integer multiple of a net current that is a difference between a first current based on a resistive memory element with the first resistance value and a second current based on a resistive memory element with the second resistance value.
2. The device of claim 1 , wherein a number of the plurality of reference memory cells along the reference line is equal to a number of the plurality of synaptic memory cells along the first output line.
3. The device of claim 1 , wherein the second resistance value is greater than the first resistance value.
4. The device of claim 1 , wherein
the synaptic memory cell comprises resistive memory elements, including the resistive memory element, corresponding to a number of bits for representing a synaptic weight assigned to the synaptic memory cell, and
the resistive memory elements corresponding to the number of bits are arranged along a same input line.
5. The device of claim 4 , wherein
the reference memory cell comprises reference memory elements, including the reference memory element, corresponding to the number of bits for representing the synaptic weight, and
the reference memory elements corresponding to the number of bits are arranged along a same input line.
6. The device of claim 1 , wherein the resistive memory elements of the synaptic memory cells connected to the first output line are connected to each other in parallel.
7. The device of claim 1 , further comprising:
another synaptic memory cell disposed along a second output line,
wherein the output circuit is configured to respectively generate output signals for each of the first output line and the second output line, using a same reference memory cell.
8. The device of claim 1 , wherein the output circuit comprises a readout circuit configured to generate a column integrated signal by integrating column bit signals for bits of the synaptic memory cell as the column signal, and generate a reference integrated signal by integrating reference bit signals for bits of the reference memory cell as the reference signal.
9. The device of claim 8 , wherein the readout circuit comprises a current mirror configured to mirror a column bit signal to generate a current of a multiple corresponding to each bit of the synaptic memory cell and each bit of the reference memory cell.
10. The device of claim 8 , wherein the output circuit is configured to generate the output signal indicating a difference between the column integrated signal and the reference integrated signal.
11. The device of claim 10 , wherein the output circuit comprises a capacitor configured to allow a current corresponding to the reference integrated signal to flow into a node and to allow a current corresponding to the column integrated signal to flow out from the node, such that a current indicating the difference between the column integrated signal and the reference integrated signal flows.
12. The device of claim 1 , wherein the output circuit comprises an analog-to-digital converter configured to convert the output signal from an analog signal to a digital value.
13. The device of claim 1 , wherein the output circuit is configured to obtain a value of a multiply-and-accumulate (MAC) between a synaptic weight and an input signal received along the input line, based on a result obtained by interpreting the output signal, and to transmit a node value determined based on the obtained value of the MAC to another neuron circuit.
14. An electronic device comprising a plurality of neural network circuits, wherein the device of claim 1 is one of the neural network circuits.
15. A method with a neural network, the method comprising:
generating a column signal based on input signals and resistive memory elements of a plurality of synaptic memory cells, to which the input signals are applied through a plurality of input lines, arranged along a first output line;
generating a reference signal based on the input signals and reference memory elements having a reference resistance value of a plurality of reference memory cells, to which the input signals are applied, arranged along a reference line with sharing the plurality of input lines with the plurality of synaptic memory cells; and
generating an output signal, for the first output line, indicating a difference between the column signal and the reference signal,
wherein the generating comprises generating, as the output signal, a current corresponding to an integer multiple of a net current that is a difference between a first current based on a resistive memory element with the first resistance value and a second current based on a resistive memory element with the second resistance value.
16. A device with a neural network, comprising:
a plurality of synaptic memory cells comprising a plurality of resistive memory elements, each having either one of a first resistance value and a second resistance value, and configured to generate a column bit signal based on input signals being received through input lines;
a plurality of reference memory cells comprising a plurality of reference memory elements, each having the second resistance value, arranged along a reference line with sharing the input lines with the plurality of synaptic memory cells, and configured to generate reference bit signal based on the input signals; and
an output circuit configured to:
generate a column integrated signal by integrating the column bit signal for each bit of the synaptic memory cell and generate a reference integrated signal by integrating the reference bit signal for each bit of the reference memory cell; and
generate an output signal corresponding to a difference between the column integrated signal and the reference integrated signal,
wherein the output circuit is configured to generate, as the output signal, a current corresponding to an integer multiple of a net current that is a difference between a first current based on a resistive memory element with the first resistance value and a second current based on a resistive memory element with the second resistance value.
17. The device of claim 16 , wherein the output circuit is configured to generate the output signal corresponding to a product between:
a value determined based on a number of the resistive memory elements having the first resistance value; and
a difference between a value of a current flowing in resistive memory elements having the first resistance value and a value of a current flowing in resistive memory elements having the second resistance value.
18. The device of claim 16 , wherein
the second resistance value is greater than the first resistance value, and
the resistive memory elements comprise a magnetic random-access memory (MRAM).
19. The device of claim 16 , wherein a number of the plurality of reference memory cells along a reference bit line is equal to a number of the plurality of synaptic memory cells along an output bit line.