In spec What dose that mean to you

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be80be

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In spec? what dose that mean to you read the data sheet and you'll find it to be not really nailed down.

Like this chip A has a max voltage rating of of 4.5 volts.
It was met to be operated at 3.3 to 3.6 volts

Now its max safe voltage it 4.5 volts

So is it 1 as long as you say under the 4.5 you'll be ok ?

Or is it 2 don't run over 3.6 volts ?

Thanks for any reply's

I'm just wanting to see how the rest of the world feels about this.
 
You can run the chip at 4.5 volts if you are willing to have the first little bump in the supply voltage fry it, or you can run it at 3.6 volts if you want it to live a long time.
 
Nice clean power we will be ok. But I didn't say run it at 4.5 But your right if we start going over the max we will have trouble in the long run. Thanks for the reply

What I'm really looking for is more like how close we can get to the maxim ratings with out going over.
 
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> how close we can get to the maxim ratings with out going over.

That's impossible to know.

For instance, take ADP3120A, a MOSFET driver.

Maximum ratings :
Bootstrap Supply Voltage Input : 35 V wrt/PGND, 40 V < 50 ns wrt/PGND

I designed to 33V max (using a small 2V safety margin). It accidentally got to 38V for a few seconds, which was clearly out of spec, and the chip survived. Either I got lucky, or the maximum ratings were conservative.
 
That specification means that it won't die at 4.5 V, but all of its other characteristics may not meet their specifications if the voltage isn't between 3.3 and 3.6 V.

If you have a logic gate rated like that, it's input and output levels would only be guaranteed when the supply is 3.3 - 3.6 V.
 
audioguru said:
why don't you use the recommended voltage range?
Click to expand...

You have to have some room to design not everything is 3.3 in the world and some times adding 10 not needed parts don't add up. Just getting ideas
 
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Looking at the specifications posted it tells me the normal range would be 3.3 to 3.6 volts with about 3.45 volts being nominal. It tells me that the maximum voltage is 4.5 volts but running at that voltage will likely degrade other parameters of the chip and the chip may have excessive heating. For ideal performance and for the chip to perform well and have a long life it should be run at a voltage between 3.3 and 3.6 volts.

Everything in design or manufacturing has allowable tolerances. They can be dimensional, electrical or other parameters but they are provided so things work as advertised.

If the maximum Ifwd of a LED is 20 mA we don't design a circuit so it runs at a maximum allowable value. WE design so the component will never (short of disaster) see a value exceeding the Maximum. When provided we also avoid minimum and work within a window of what is allowed.

Just My Take
Ron
 
I always remember what one of my prof's said "current kills"
current creates heat and that's what kills the chip
personally i'd use the 3.6V so i don't under supply, and would only use the max voltage rating if I had to "squeeze it in"

what i'v always wondered is: if you brought up the voltage to double max, but kept the current at spec, would the chip still operate??
 
Chances are it would be zapped.

Your prof was only half right. It isn't just current that kills, but the power (current times voltage).
 
Your prof was only half right. It isn't just current that kills, but the power (current times voltage)
Click to expand...
LOL

It like a car voltage is the gas no gas no go

Current like the engine little engine little power

Where the load big load little engine not much will happen

But little load big engine and who no's what will happen.
 
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The maximum may be rated with a heatsink and under MAX load.

For instance, if a uC has 4 i/o pins that can sink 25ma per pin on 100ma total, if you are sinking 100ma, you will likely fry the uC if powered at 4.5v for any length of time.

Also, accuracy of the ADC or I2C can only be reliable to 4.5v at 4.6v you may speed up a RC osc and throw timing off.
 
Why even have maxim spec If most don't believe you can used that information to design with ? I haven't seen to many company's That don't push to the limits a part or two. LOL

And I sure have seen some dumb data sheets looks like some one made a generic data sheet and just change name to make you think it's new LOL

If I make say a Amp for small set of speakers for the computer. I'm sure not going to say here you go I hope it works LOL I'm going to test the amp till it breaks Just to no where I stand in the long run.
 
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be80be said:
Why even have maxim spec If most don't believe you can used that information to design with ? I haven't seen to many company's That don't push to the limits a part or two. LOL
Click to expand...
The purpose of the Absolute Maximum spec is to tell you when the device is likely to fail so you can do the design to insure that these maximums are never exceeded. The nominal voltage values are what you normally use since that is where the device is designed to meet its operational specifications.

If you want to push the limits, you can, but that can lead to a circuit that doesn't meet specs and/or has a reduced lifetime.
 
If you want to talk about bad specs, look at mosfets. The large print on the data sheet gives a large amperage and voltage number. But when you read the fine print in the notes, the wattage is limited to way lower than the wattage in the bold print. All for marketing
 
The voltage and current limits given in the MOSFET data sheets are valid. But that doesn't imply that you can apply them simultaneously since that would exceed the power rating of the chip. You can't take any one spec limit in isolation, you have to consider them all. I don't think that's particularly a marketing ploy.
 
be80be-
You have to have some room to design not everything is 3.3 in the world and some times adding 10 not needed parts don't add up. Just getting ideas
Click to expand...

Here's an idea; If the 3.3v IC only requires low current (and many do) just power it through any typical LED that gives a 1.7v forward voltage drop. That converts 5v to 3.3v. You should also use a 0.1uF cap on the IC power pins.

So that's 2 parts not 10, and 2 parts you should always have for free in your junk box.
 
Thats a good one Mr RB +1

You might what to spec that at 20ma MAX.
 
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