I'm using LMC6482 opamp with +/-15V rail voltages and having weird behavior. This means Vcc is +15V and Vee is -15V in my case.
Am I exceeding the specs? The jargon in the datasheet is not clear or should I say I'm not familiar with it.
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\$\begingroup\$ You could do 15V and 0V, but that probably won't meet your needs. \$\endgroup\$ – StainlessSteelRat Nov 23 '18 at 17:18
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Yes, you are exceeding the specs. Look at table 6.1 of the DATASHEET on page 3:
It clearly states the maximum difference between the V+ and V- pins is 16V. This means you can have +8V and -8V, as the difference is 16V.
As you have it right now, your difference is 30V, which is almost double the maximum ratings. Chances are, you have damaged the op-amp and it will need to be replaced. You should ALWAYS check the maximum ratings of any IC you are using if you are worried. If you can, try and be within the maximum, so +7.5V and -7.5V would work nicely here, for a total of 15V supply.
Although directly under the Absolute Maximum Ratings, it does state:
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
Some people new to electronics could take the maximum to mean that is what is OK to use. The other bit that should be looked at is the Recommended Operating Conditions:
Making sure you stay above and below the min/max should make sure the device works as specified, however, the Absolute Maximum Ratings table should always be checked too.
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4\$\begingroup\$ OP did check the maximum ratings, but was confused. And it seems to be guaranteed to function well for a 15 volt supply, so ±7.5 would be nice. \$\endgroup\$ – pipe Nov 23 '18 at 13:41
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10\$\begingroup\$ "The jargon in the datasheet is not clear" sounds to me like he actually read it but did not understand it. \$\endgroup\$ – pipe Nov 23 '18 at 13:49
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4\$\begingroup\$ Also worth noting that the chip is designed for a nominal supply voltage of 3V, 5V, or 15V. 16V is the absolute maximum but it should not be the design voltage. We never design to absolute maximums - we usually design with safety margins specifically to avoid them. \$\endgroup\$ – J... Nov 23 '18 at 18:21
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8\$\begingroup\$ "You should ALWAYS check the maximum ratings" - NO NO NO. You should check the (recommended) operating conditions! Please don't point anyone (especially not newbies) at the absolute maxima. \$\endgroup\$ – Wouter van Ooijen Nov 23 '18 at 22:47
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1\$\begingroup\$ I would think it's a given that you don't go all the way to the maximum. That's why you check them. You should always check the maximum to make sure you stay within them \$\endgroup\$ – MCG Nov 23 '18 at 22:52
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Figure 1. Vmax.
This line of the datasheet is stating that the maximum voltage difference between V+ and V- is 16 V.
You have probably damaged the op-amp.
answered Nov 23 '18 at 13:34
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\$\begingroup\$ Oh I thought it is +16 to -16. :(( And it is damaged yes it doesn't function as it supposed to. \$\endgroup\$ – atmnt Nov 23 '18 at 13:35
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1\$\begingroup\$ I've never seen it written that way before but I take it to mean you can run it 0/16V or -16/0 V or -5/+5 or any other combination provided that it's 16 V max from one to the other. Sorry for your loss! \$\endgroup\$ – Transistor Nov 23 '18 at 15:27
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1\$\begingroup\$ "you can run it 0/16V or -16/0 V or -5/+5 or any other combination provided that it's 16 V max from one to the other." Absolute maximum ratings should not be used for normal operation, so 0/15V or .15/0 V or -7/+7 V or a lower voltage. \$\endgroup\$ – Uwe Nov 24 '18 at 15:04
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I read your question as "yes I've read the datasheet, but its unclear". So let's address how to read the supply voltage range specification as the manufacturer Texas Instruments write it in their original product data sheet:
Supply Voltage (V+ - V-)... MAX 16V
You have a V+ of 15V and a V- of -15V. Now we use the formula from the data sheet and get:
(15 - (-15)) = 15 + 15 = 30V
That's the way to interpret this voltage range specification. So yes, you are exceeding specified maximum supply voltage range by 14V.
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Other answers mentione the asbsolute maximum ratings, which is NOT what youy should look for when designing a functional system. Instead, you should use the recommended operating conditions. In this case, those specify 15.5V.
In your case, you could check the absolute maxima to find out whether your chip had a chance of survival. As others have pointed out, that is not the case.
answered Nov 23 '18 at 22:46
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3\$\begingroup\$ Finally the only one answer using the recommended operating conditions! So the opamp may be used with very low voltages too, for instance -2/+2 V or 0/4 V. When reading a datasheet it is very important to look for both absolute maximum ratings and recommended operating conditions and read and respect them both. When using -7.5/+7.5 V, spikes on supply voltages should not exceed 0.25 V. \$\endgroup\$ – Uwe Nov 24 '18 at 15:12
