Coin size batteries on circuit boards used for?

#12

Joined Nov 30, 2010
18,224
SAM! The only "chips" that "need" the "batteries" (usually cells, not batteries) are ones that somebody WANTED to have constant or backup power to -> for a SPECIFIC task<- !

Tell us what you want done, or what the system designer of a specific system was trying to do, and we'll say "yep, a battery (or cell) is what you'd want there!
Sam doesn't want specific answers to specific circuits. He wants universal answers that work all the time for all circuits.
 

Thread Starter

SamEricson

Joined Apr 25, 2015
196
all im sure you guys have seen many circuit boards with these coins size batteries , I was just wondering what kinds and types of Chips theses batteries went to.
 

MrCarlos

Joined Jan 2, 2010
400
Hello SamEricson

Continuing in the circle.

The USE or NON-USE of batteries do not depend on the kinds of Chips but the effect of losing it's internal information when they are disconnected from the main power.
For example, a chip containing TTL family Flip-Flip's. If you do not want to lose its current state, In this case a battery could be used.
When the main power is cut, the battery continues to supply power to not get lost the current state of the Flip-Flip's.
That is, if you do not want to miss:
Code.
Data.
Time of day.
Actual state.
Etc.
We use a battery.
And we can use any kind of device: CMOS, TTL, NMOS, Etc.
Including complete systems that we do not want to stop but the energy in the wall contact is interrupted.
 

Thread Starter

SamEricson

Joined Apr 25, 2015
196
The USE or NON-USE of batteries do not depend on the kinds of Chips but the effect of losing it's internal information when they are disconnected from the main power.
Yes true i understand that part

So what you're saying is that i can hook up a backup battery to any RAM chip or flip flop chip

Why do they use backup batteries for NVRAM chips instead of RAM chips? I have never seen a battery for a RAM chip only for NVRAM chips

I can't hook up a battery to a ROM chip or EEPROM chip or a Logic gate, it won't do any purpose
 

BillB3857

Joined Feb 28, 2009
2,570
A dynamic ram will need to be refreshed to maintain memory. The refresh is handled by other parts of the circuit, so NO, you cannot just connect a battery to ANY RAM chip and have it retain data.
Once more around the block!
 

WBahn

Joined Mar 31, 2012
29,978
Yes true i understand that part

So what you're saying is that i can hook up a backup battery to any RAM chip or flip flop chip.
Yes, in theory. It's called battery-backed RAM. Works best with SRAM. If you package a memory controller you could do it with DRAM, but you largely defeat the purpose because now you are rapidly draining the battery.

Why do they use backup batteries for NVRAM chips instead of RAM chips?
They use a battery if one is needed to make it non-volatile. And they do use batteries with RAM chips -- to make NVRAM out of it.

I have never seen a battery for a RAM chip only for NVRAM chips
Look up battery-backed RAM.

I can't hook up a battery to a ROM chip or EEPROM chip or a Logic gate, it won't do any purpose
Depends on what you want it to do.


Most NVRAM technologies do NOT use batteries. NVRAM is merely Non-volatile Random Access Memory. If you are talking about component-level technologies, then NVRAM refers to technologies, such as floating-gate CMOS, that are intrinsically non-volatile. No battery needed. At the assembly level you can pair RAM and a battery and call the assembly NVRAM because, so the user, it appears indistinguishable.
 

Thread Starter

SamEricson

Joined Apr 25, 2015
196
It's called battery-backed RAM. Works best with SRAM. If you package a memory controller you could do it with DRAM,
So static RAM can use a backup battery
Dynamic Ram needs a memory controller to use a backup battery
 

WBahn

Joined Mar 31, 2012
29,978
So static RAM can use a backup battery
Dynamic Ram needs a memory controller to use a backup battery
You need a memory controller (or, more specifically, a DRAM controller) with DRAM because it is DRAM -- unlike static RAM, dynamic RAM loses its contents even while it is powered. It has to be periodically refreshed (typically 15 times a second or so). But that consumes power which will quickly drain any reasonable battery for most applications. So in practice you use battery-backed SRAM because SRAM that is not being read from or written to draw zero power (only a tiny amount of leakage current) so that a battery being used to back SRAM will last almost as long as it would have lasted sitting in an unopened package of batteries.
 
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