Neuromorphic memory circuit using a leaky integrate and fire (LIF) line to transmit axon LIF pulse and a conductive denrite LIF line

Patent metadata

Field	Value
Publication number	US-9830981-B2
Application number	US-201514596223-A
Country	US
Kind code	B2
Filing date	Jan 14, 2015
Priority date	Jan 14, 2015
Publication date	Nov 28, 2017
Grant date	Nov 28, 2017

Abstract

A neuromorphic memory circuit including a programmable resistive memory element, an axon LIF line to transmit an axon LIF pulse, and a dendrite LIF line to build up a dendrite LIF charge over time. A first transistor provides a discharge path for the dendrite LIF charge through the programmable resistive memory element when the axon LIF line transmits the axon LIF pulse. An axon STDP line transmits an axon STDP pulse. The axon STDP pulse is longer than the axon LIF pulse. A dendrite STDP line is configured to transmit a dendrite STDP pulse after voltage at the dendrite LIF line falls below a threshold voltage. A second transistor is coupled to the axon STDP line and the programmable resistive memory element. The second transistor provides an electrical path for the dendrite STDP pulse through the programmable resistive memory element when the axon STDP line transmits the axon STDP pulse.

First claim

What is claimed is:

1. A neuromorphic memory circuit comprising:
a programmable resistive memory element;
a conductive axon leaky integrate and fire (LIF) line configured to transmit an axon LIF pulse;
a conductive dendrite LIF line configured to build up a dendrite LIF charge over time;
a first transistor electrically coupled to the dendrite LIF line and the programmable resistive memory element, the first transistor providing a discharge path for the dendrite LIF charge through the programmable resistive memory element when the axon LIF line transmits the axon LIF pulse;
a conductive axon spike timing dependent plasticity (STDP) line configured to transmit an axon STDP pulse, the axon STDP pulse being longer than the axon LIF pulse;
a conductive dendrite STDP line configured to transmit a dendrite STDP pulse after voltage at the dendrite LIF line falls below a threshold voltage; and
a second transistor electrically coupled to the axon STDP line and the programmable resistive memory element, the second transistor providing an electrical path for the dendrite STDP pulse through the programmable resistive memory element when the axon STDP line transmits the axon STDP pulse.

2. The neuromorphic memory circuit of claim 1 , further comprising:
a leak resistor coupled to a source voltage; and
an integration capacitor coupled to the leak resistor, the integration capacitor configured to build up the dendrite LIF charge over time.

3. The neuromorphic memory circuit of claim 1 , further comprising:
an axon LIF pulse generator for generating the axon LIF pulse, the axon LIF pulse generator electrically coupled to the conductive axon LIF line;
an axon STDP pulse generator for generating the axon STDP pulse, the axon STDP pulse generator electrically coupled to the conductive axon STDP line; and
a dendrite STDP pulse generator for generating the dendrite STDP pulse, the dendrite STDP pulse generator electrically coupled to the dendrite STDP line.

4. The neuromorphic memory circuit of claim 1 , further comprising a comparator electrically coupled to the dendrite LIF line and the threshold voltage, the comparator configured to compare voltage at the dendrite LIF line and the threshold voltage.

5. The neuromorphic memory circuit of claim 1 , further comprising a third transistor in series circuit with the second transistor, the third transistor configured to prevent creation of the discharge path for the dendrite LIF charge through both the first transistor and the second transistor.

6. The neuromorphic memory circuit of claim 1 , wherein the programmable resistive memory element includes a phase change material.

7. The neuromorphic memory circuit of claim 6 , wherein the phase change material has an electrical resistance and is programmable to a set state having a set electrical resistance and reset state having a reset electrical resistance at least a factor of 10 greater than the set electrical resistance, the phase change material includes an initial state having an initial electrical resistance between the set electrical resistance and the reset electrical resistance, the initial state is at a lower potential energy than the set state and the reset state such that the electrical resistance of the phase change material programmed to the set state or the reset state drifts toward the initial electrical resistance over time.

8. The neuromorphic memory circuit of claim 7 , wherein the phase change material includes Ge x Sb y Te z , where a Ge atomic concentration x is within a range from 30% to 70%, a Sb atomic concentration y is within a range from 10% to 30%, and a Te atomic concentration z is within a range from 20% to 50%.

9. A neuromorphic memory circuit comprising:
a memory cell array, each memory cell in the memory cell array including:
a programmable resistive memory element;
a conductive axon leaky integrate and fire (LIF) line configured to transmit an axon LIF pulse, the axon LIF line electrically coupled to a column of memory cells in the memory cell array;
a conductive dendrite LIF line configured to build up a dendrite LIF charge over time, the dendrite LIF line electrically coupled to a row of memory cells in the memory cell array;
a first transistor electrically coupled to the dendrite LIF line and the programmable resistive memory element, the first transistor providing a discharge path for the dendrite LIF charge through the programmable resistive memory element when the axon LIF line transmits the axon LIF pulse;
a conductive axon spike timing dependent plasticity (STDP) line configured to transmit an axon STDP pulse, the axon STDP pulse being longer than the axon LIF pulse, the axon STDP line electrically coupled to the column of memory cells in the memory cell array;
a conductive dendrite STDP line configured to transmit a dendrite STDP pulse after voltage at the dendrite LIF line falls below a threshold voltage, the dendrite STDP line electrically coupled to the row of memory cells in the memory cell array; and
a second transistor electrically coupled to the axon STDP line and the programmable resistive memory element, the second transistor providing an electrical path for the dendrite STDP pulse through the programmable resistive memory element when the axon STDP line transmits the axon STDP pulse.

10. The neuromorphic memory circuit of claim 9 , further comprising:
a leak resistor coupled to a source voltage; and
an integration capacitor coupled to the leak resistor, the integration capacitor configured to build up the dendrite LIF charge over time.

11. The neuromorphic memory circuit of claim 9 , further comprising:
an axon LIF pulse generator for generating the axon LIF pulse, the axon LIF pulse generator electrically coupled to the conductive axon LIF line;
an axon STDP pulse generator for generating the axon STDP pulse, the axon STDP pulse generator electrically coupled to the conductive axon STDP line; and
a dendrite STDP pulse generator for generating the dendrite STDP pulse, the dendrite STDP pulse generator electrically coupled to the dendrite STDP line.

12. The neuromorphic memory circuit of claim 9 , further comprising a comparator electrically coupled to the dendrite LIF line and the threshold voltage, the comparator configured to compare voltage at the dendrite LIF line and the threshold voltage.

13. The neuromorphic memory circuit of claim 9 , wherein each memory cell in the memory cell array includes a third transistor in series circuit with the second transistor, the third transistor configured to prevent creation of the discharge path for the dendrite LIF charge through both the first transistor and the second transistor.

14. The neuromorphic memory circuit of claim 9 , wherein the programmable resistive memory element includes a phase change material.

15. The neuromorphic memory circuit of claim 14 , wherein the phase change material has an electrical resistance and is programmable to a set state having a set electrical resistance and reset state having a reset electrical resistance at least a factor of 10 greater than the set electrical resistance, the phase change material includes an initial state having an initial electrical resistance between the set electrical resistance and the reset electrical resistance, the initial state is at a lower potential energy than the set state and the reset state such that the electrical resistance of the phase change material programmed to the set state or the reset state drifts toward the initial electrical resistance over time.

Assignees

• IBM

Inventors

• Kim Sangbum
• Lam Chung H

Classifications

• G11C11/54 Primary

  using elements simulating biological cells, e.g. neuron · CPC title

• G06N3/063 Primary

  using electronic means · CPC title

• G06N3/088

  Non-supervised learning, e.g. competitive learning · CPC title

• G06N3/049

  Temporal neural networks, e.g. delay elements, oscillating neurons or pulsed inputs · CPC title

• G11C27/00

  Electric analogue stores, e.g. for storing instantaneous values · CPC title