This document discusses different types of memory and array structures used in VLSI design. It covers the basics of SRAM, DRAM, ROM, flash memory and emerging non-volatile memories. Key considerations for memory design like speed, size, power consumption and reliability are discussed. Different memory array organizations and access schemes are also summarized. The document concludes by describing various array structures like logic, analog, processor and sensor arrays. Optimization techniques for VLSI design are briefly covered.

1. Designing Memory And
Array Structures
Mr.K.Yogeshwaran KIT-CBE

2. Introduction
Memories are one of the most useful VLSI building
blocks. One reason for their utility is that memory
arrays can be extremely dense. This density results
from their very regular wiring.

3. Types of Memories
● SRAM (Static Random-Access Memory)
● DRAM (Dynamic Random-Access Memory)
● ROM (Read-Only Memory)
● Flash Memory
● Emerging Non-volatile Memories (e.g., MRAM, PCM)

4. Key Memory Design Considerations
● Speed vs. size trade-offs
● Power consumption
● Read and write latencies
● Data integrity and reliability

5. SRAM Design
SRAM uses a flip-flop circuit to store each data bit.
The circuit delivers two stable states, which are read
as 1 or 0. To support these states, the circuit requires
six transistors, four to store the bit and two to control
access to the cell.

6. DRAM Design
● Dynamic random access memory (DRAM) is a
type of semiconductor memory that is typically
used for the data or program code needed by a
computer processor to function.
● DRAM is a common type of random access
memory (RAM) that is used in personal computers
(PCs), workstations and servers.

7. ROM and Flash Memory Design
● Flash memory is a type of non-volatile memory
that can store data even when the power is off.
It is widely used in devices such as smartphones,
cameras, USB drives, and solid-state drives
(SSDs).
● Flash memory is based on the principle of using
electric charges to store bits of information in
cells.

8. Emerging Non-volatile Memories
Emerging nonvolatile memory technologies such as magnetic
● Random-access memory (MRAM)
● Spin-transfer torque random-access memory (STT-RAM)
● Ferroelectric random-access memory (FeRAM)
● Phase-change memory (PCM)
● Resistive random-access memory (RRAM)

9. Memory Array Organization
● A memory array is a linear data structure that
stores a collection of similar data types at
contiguous locations in a computer's memory.
● Memory arrays are categorized as one-
dimensional arrays and multiple-dimensional
arrays.

10. Memory Access Schemes
● Random access
● Serial access
● Pipelined access

11. Memory Optimization
● VLSI enables the miniaturization, optimization,
and integration of various components and
functions on a single chip, such as logic,
memory, analog, and digital circuits.
● Flash memory is one of the applications of VLSI
technology, as it allows creating high-density, low-
power, and fast memory devices.

12. APPLICATIONS
● VLSI-based chips are used in routers, modems,
base stations, and network switches to enable
fast and reliable data transmission.
● VLSI technology has had a significant impact on
healthcare, enabling the development of medical
imaging devices, wearable health monitors, and
implantable medical devices

13. Array Structures
● An array is a group of variables having the same
data type. It can be accessed using an index
value.
● An index is a memory address and the array value
is stored at that address.

14. Types of Array Structures
● Memory Arrays
● Logic Arrays
● Analog Arrays
● Processor Arrays
● Sensor Arrays
● Memory Hierarchiesa

15. Memory Arrays
● Memory arrays are built as an array of bit cells,
each of which stores 1 bit of data.
● The each bit cell is connected to a wordline and a
bitline.
● For each combination of address bits, the memory
asserts a single wordline that activates the bit
cells in that row.

16. Logic Arrays
● The PLA (Programmable Logic Array) has
programmable connections for both AND and OR
arrays.
● So it is the most flexible type of PLD. generate a
product term of the input variables and does not
generate all the minterms as in the ROM.

17. Analog Arrays
A field-programmable analog array (FPAA) is an
integrated circuit device containing computational
analog blocks (CAB) and interconnects between these
blocks offering field-programmability.

18. Processor Arrays
● A processor that performs computations on a vast
array of data is known as an array processor.
● Multiprocessors and vector processors are other
terms for array processors.
● It only executes one instruction at a time on an
array of data.

19. Sensor Arrays
A sensor array is a group of sensors, usually deployed
in a certain geometry pattern, used for collecting and
processing electromagnetic or acoustic signals.

20. Optimization Techniques
● Optimization consists of three steps viz.
Architectural, Logic level and Gate level
optimization.
● Optimization is based on HDL coding style and
constraints set.