Re: Confused: What is difference between SRAM and Flash Card
Hitesh Brahmbhatt (hitesh@opti.com)
Thu, 12 Dec 96 10:25:47 PST
> From owner-ogo@lifelike.com Wed Dec 11 19:45:35 1996
> From: "Jake" <tbush@atlantis.nconnect.net>
> To: <ogo@lifelike.com>
> Subject: Re: Confused: What is difference between SRAM and Flash Card
> Date: Fri, 13 Dec 1996 20:24:00 -0600
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> I have another question about Flash Cards. How do they work??? I know (I
> think) that a SRAM/RAM stores information by electricly charging millions
> of mini capacitors and those capacitors need power to hold there charge.
> And I think I understand how ROM works. Its info that is permanently
> burned into an IC chip right? But what about flash? Is it an IC Chip that
> info can be burned into over and over? I dont understand how it can keep
> data with no power (its solid state right?).
>
>
Well, it is very similar to E2PROM(Electrically Erasable-Programmable ROM). In
Flash sufficiently high voltages are applied on the GATE(sorry for CMOS-talk;)
structure to shoot the electrons through insulating Silicon Oxide and then this
charge remain trapped in insulating material(which is similar to capacitor; except
no active supply is needed). Voltage with opposite polarity serves to deplete that
charge when the location needs to be erased.
Of course the whole thing is not as simple as described above but that is the basic
Principle. And for Techno-geeks like me that Shooting of Electrons through insulating
Oxide is called "Tunnelling" in semiconductor jargon.
Hope it was enjoyable ;)
Hitesh