Sum-of-products accelerator array

• US 10,719,296 B2
• Filed: 01/17/2018
• Issued: 07/21/2020
• Est. Priority Date: 01/17/2018
• Status: Active Grant

• Current Assignee: Macronix International Co., Ltd.
• Original Assignee: Macronix International Co., Ltd.
• Inventors: Lee, Feng-Min, Lin, Yu-Yu
• Primary Examiner(s): Mai, Tan V
• Application Number:
  US15/873,369
• Publication Number:
  US 20190220249A1
• Time in Patent Office: 916 Days
• Field of Search: 708603
• CPC Class Codes: G06F 2207/4814 Non-logic devices, e.g. operational amplifiers
• CPC Class Codes: G06F 7/5443 Sum of products for applications thereof, see the relevant places, e.g. G06F17/10, H03H17/00
• CPC Class Codes: G11C 11/54 using elements simulating biological cells, e.g. neuron
• CPC Class Codes: G11C 16/0483 comprising cells having several storage transistors connected in series
• CPC Class Codes: H03K 19/17708 using an AND matrix followed by an OR matrix, i.e. programmable logic arrays
• CPC Class Codes: H10B 41/35 with a cell select transistor, e.g. NAND
• CPC Class Codes: H10B 43/35 with cell select transistors, e.g. NAND
• CPC Class Codes: H10N 70/253 having three or more terminals, e.g. transistor-like devices

Abstract

A device for generating sum-of-products data includes an array of variable resistance cells, variable resistance cells in the array each comprising a programmable threshold transistor and a resistor connected in parallel, the array including n columns of cells including strings of series-connected cells and m rows of cells. Control and bias circuitry are coupled to the array, including logic for programming the programmable threshold transistors in the array with thresholds corresponding to values of a weight factor W_mn for the corresponding cell. Input drivers are coupled to corresponding ones of the m rows of cells, the input drivers selectively applying inputs X_m to rows m. Column drivers are configured to apply currents I_n to corresponding ones of the n columns of cells. Voltage sensing circuits operatively coupled to the columns of cells.

Claims

1. A device for generating sum-of-products, comprising:

an array of variable resistance cells, variable resistance cells in the array each comprising a programmable threshold transistor and a resistor connected in parallel, the array including n columns of cells including strings of series-connected cells and m rows of cells, the programmable threshold transistors in the array having thresholds corresponding to values of a weight factor W_mn for the corresponding cell;

m input drivers coupled to corresponding ones of the m rows of cells, the input drivers selectively applying inputs X_m to more than one of the m rows in parallel;

n column drivers applying currents I_n to corresponding ones of the n columns of cells to produce a voltage representing a sum of products of the inputs X_m applied to the more than one of the m rows and the weight factors W_mn for the cells; and

voltage sensing circuits operatively coupled to the n columns of cells to sense the voltage representing the sum of products.

2. The device of claim 1, wherein the programmable threshold transistors are charge trapping memory transistors, and including control and bias circuitry coupled to the array configured to apply program bias voltages to programmable resistance cells in the array to selectively set the threshold in the programmable threshold transistors in the cells.

3. The device of claim 2, wherein the resistor in the variable resistance cell comprises a buried implant resistor in the charge trapping memory transistor.

4. The device of claim 2, wherein the programmable threshold transistors in the variable resistance cells are floating gate charge trapping transistors, and the resistor in the variable resistance cell comprises a buried implant resistor in the floating gate charge trapping transistor.

5. The device of claim 2, wherein the programmable threshold transistors in the variable resistance cells are dielectric charge trapping transistors, and the resistor in the variable resistance cell comprises a buried implant resistor in the dielectric charge trapping transistor.

6. The device of claim 1, wherein cells in the array are configured into functional sets including two or more members, implementing respective terms X_iW_i of a sum-of-products function, each functional set receiving a corresponding term input X_i and term weight W_i, the term weight being a function of the programmable thresholds of the two or more members of the functional set.

7. The device of claim 1, wherein cells in the array are configured into a functional set including a plurality of members connected in series on column n, and the resistors in the cells in the functional set have different values of resistance, the functional set implementing a term X_iW_i of a sum-of-products function, receiving a corresponding term input X_i and having term weight W_i, the term weight being a function of the programmable thresholds of the plurality of members of the functional set, the term input being coupled to all members in the plurality of members in the functional set.

8. The device of claim 1, wherein cells in the array are configured into a functional set including a plurality of members arranged on different columns in the array, and the resistors in the cells in the functional set have different values of resistance, the functional set implementing a term X_iW_i of a sum-of-products function, receiving a corresponding term input X_i and having term weight W_i, the term weight being a function of the programmable thresholds of the plurality of members of the functional set;

and

the voltage sensing circuits include voltage summing circuits operably connected to the sum voltages generated on columns of cells in the functional set.

9. The device of claim 8, wherein the voltage sensing circuits apply fixed ratios of weight factors in the summing to the voltages on the different columns, the term weight being a function of the programmable thresholds of the plurality of members of the functional set and of the fixed ratios.

10. The device of claim 1, wherein cells in the array are configured into a functional set including plural strings of multiple cells, the plural strings being arranged on different columns in the array, and the n column drivers applying currents I_n to corresponding ones of the n columns of cells and applying different magnitudes of current to the different columns, the functional set implementing a term X_iW_i of a sum-of-products function, receiving a corresponding term input X_i and having term weight W_i, the term weight being a function of the programmable thresholds of the plurality of members of the functional set and the different magnitudes of current;

and

the voltage sensing circuits include voltage summing circuits operably connected to the sum voltages generated on columns of cells in the functional set.

11. The device of claim 1, wherein cells in the array are configured into a functional set including cells arranged on different columns in the array, the resistors in the cells in the functional set having different values of resistance, and the n column drivers applying currents I_n to corresponding ones of the n columns of cells and applying different magnitudes of current to the different columns, the functional set implementing a term X_iW_i of a sum-of-products function, receiving a corresponding term input X_i and having term weight W_i, the term weight being a function of the programmable thresholds of the plurality of members of the functional set, the different values of resistance, and the different magnitudes of current;

and

the voltage sensing circuits include voltage summing circuits operably connected to the sum voltages generated on columns of cells in the functional set.

12. The device of claim 1, wherein, the array includes a reference column of cells configured to generate a column reference voltage;

the device including;

a circuit to generate sensing reference voltages as a function of the column reference voltage; and

wherein the voltage sensing circuits include comparators configured to compare voltages on selected columns of cells with the sensing reference voltages to generate outputs indicating voltage levels on the selected columns.

13. The device of claim 1, wherein the array includes a first reference column of cells configured to generate a low column reference voltage and a second reference column of cells configured to generate a high column reference voltage;

the device including;

a circuit to generate sensing reference voltages as a function of the high and low column reference voltages; and

wherein the voltage sensing circuits include comparators configured to compare voltages on selected columns of cells with the sensing reference voltages to generate outputs indicating voltage levels on the selected columns.

14. A method for operating an array of variable resistance cells, variable resistance cells in the array each comprising a programmable threshold transistor and a resistor connected in parallel, the array including n columns of cells including strings of series-connected cells and m rows of cells, to produce sum-of-products data, comprising:

programming the programmable threshold transistors in the array having thresholds corresponding to values of a weight factor W_mn for the corresponding cell;

selectively applying inputs X_m to more than one of the m rows in parallel;

applying currents I_n to corresponding ones of the n columns of cells to produce a voltage representing a sum of products of the inputs X_m applied to the more than one of the m rows and the weight factors W_mn for the cells; and

sensing voltages on one or more of the n columns of cells.

15. The method of claim 14, including configuring cells in the array into functional sets of cells including two or more members, implementing respective terms X_iW_i of a sum-of-products function, each functional set receiving a corresponding term input X_i and term weight W_i, the term weight being a function of the programmable thresholds of the two or more members of the functional set.

16. The method of claim 14, including configuring cells in the array into a functional set including a plurality of members connected in series on column n, wherein the resistors in the cells in the functional set have different values of resistance, the functional set implementing a term X_iW_i of a sum-of-products function, receiving a corresponding term input X_i and having term weight W_i, the term weight being a function of the programmable thresholds of the plurality of members of the functional set, the term input being coupled to all members in the plurality of members in the functional set.

17. The method of claim 14, including configuring cells in the array into a functional set including a plurality of members arranged on different columns in the array, wherein the resistors in the cells in the functional set have different values of resistance, the functional set implementing a term X_iW_i of a sum-of-products function, receiving a corresponding term input X_i and having term weight W_i, the term weight being a function of the programmable thresholds of the plurality of members of the functional set;

and

summing voltages generated on columns of cells in the functional set.

18. The method of claim 14, including configuring cells in the array into a functional set including plural strings of multiple cells, the plural strings being arranged on different columns in the array, and applying currents I_n to corresponding ones of the n columns of cells and applying different magnitudes of current to the different columns, the functional set implementing a term X_iW_i of a sum-of-products function, receiving a corresponding term input X_i and having term weight W_i, the term weight being a function of the programmable thresholds of the plurality of members of the functional set and the different magnitudes of current;

and

summing voltages generated on columns of cells in the functional set.

19. The method of claim 14, including configuring cells in the array into a functional set including cells arranged on different columns in the array, wherein the resistors in the cells in the functional set have different values of resistance, and applying different magnitudes currents I_n to the different columns, the functional set implementing a term X_iW_i of a sum-of-products function, receiving a corresponding term input X_i and having term weight W_i, the term weight being a function of the programmable thresholds of the plurality of members of the functional set, the different values of resistance, and the different magnitudes of current;

and

summing voltages generated on columns of cells in the functional set.

20. The method of claim 14, including:

using a reference column of cells to generate a column reference voltage;

generating sensing reference voltages as a function of the column reference voltage; and

comparing voltages on selected columns of cells with the sensing reference voltages to generate outputs indicating voltage levels on the selected columns.