优选FlashMemory测试简介

Magnetic – Magnetic disk and tape can be easily programmed and erased by user, but are slower than Flash.
Optical – CD ROM can be easily programmed by user but is slower than Flash.
“1”
Bit line Bit line Bit line
Simple EPROM Memory Array
Sense Amps / Buffers
Word line
Floating gate
A second “floating gate” serves as the storage element in an EPROM.
优选FlashMemory测试简 介
Unit 1: Introduction to Flash Technology
Overview of Memory Devices
Course Contents
Two Basic Memory Categories
Volatile Memory 易挥发存储器
–Buffer on column sense amps
Word line
Sense Amps / Buffers
Capacitor
Currentsensing line
Capacitor charged, No current,
“0”
Capacitor uncharged, Current flow,
Basic Flash Memory Cell
Source
Gate Floating Gate
Drain
Floating Gate (electrically isolated) is the storage element • charged = “programmed” • neutral = “erased”
• DRAM - Dynamic RAM is commonly used for read-write memory in computers.
Nonvolatile Memory
ROM – Read Only Memory, ROM, are programmed in a wafer fab and cannot be erased or reprogrammed in the field.
• Data is lost when power is removed.
Nonvolatile Memory非易挥发存储器
• Data remains even when power is removed.
Volatile Memory
RAM – Random Access Memory
• SRAM - Static RAM is commonly used as 640 Kb cache memory in computers.
Benefits of Flash Memory Chips
Smaller than EPROMS and EEPROMS Requires only one transistor and a storage
capacitor per bit cell. Can be quickly and easily erased and
reprogrammed without the need of special equipment. Excellent for use in cell phones, pagers, calculators, portable digital devices, automotive, flight data recorders, and personal computers.
Polysilicon (doped)
n+ Drain
Bit line Bit line Bit line
•Activate Row to read
–If capacitor was charged, no current flows on bit line
–If capacitor not charged, current flows on bit line
Simple ROM Memory Array
Word line
Data “0” Cell No gate metal contact
G S
Bit liБайду номын сангаасe D
Data “1” Cell Gate is connected
Word line
Bit line
G
S
D
Simple DRAM Memory Array
EEPROM – Electrically Erasable PROM can be erased with higher voltages and reprogrammed in the field.
Nonvolatile Memory
NVRAM – Nonvolatile RAM (Flash) is smaller than PROMs, less expensive, and easier to program and erase.
PROM – Programmable ROM can be reprogrammed in the field by applying larger voltages with special equipment.
EPROM – Erasable PROM can be erased with UV light and reprogrammed with special equipment.
Flash Cell Structure - Similar to EPROM, except Electrically-erasable
Dielectric (ONO) Dielectric (oxide)
n+ Source
Control Gate Floating Gate
p+ Substrate