Running opamp on Vcc above absolute maximum - Page 1
Forum section: electronics / projects

author: dobsonr741
author_rank: Frequent Contributor
timestamp: May 26, 2023, 05:46:09 pm
content: Curious what others experienced when crossing over opamps absolute max Vcc rating. Experimented with TLV321, having Vcc max of 5.5V.Seems quiescent current increase is proportional with Vcc increase until 7V, then slightly increases the ratio, and at 10V it goes 100x to 30mA.Did not stress beyond that point, and the part is still working fine under the normal 5V. I'm planning to use it at 6V. What's the prediction, how long it's going to last?

author: Algoma
author_rank: Frequent Contributor
timestamp: May 26, 2023, 05:57:33 pm
content: who is the manufacturer? The LMV321 from ST is rated up to 7V VCChttps://www.st.com/resource/en/datasheet/lmv321.pdfBeyond that, it will generally slowly destory the function of the IC, breaking down the gates, forcing electrons across barriers they're not supposed to cross. That leakage will increase over time, until it fails completely.

author: Algoma
author_rank: Frequent Contributor
timestamp: May 26, 2023, 06:08:09 pm
content: Overvolt an electrlytic capacitor (wear safety glasses) if you want a visual demonstration of what you're doing to that chip.You'll see current leakage begin at a point exceeding its rated voltage, higher for quality capacitors, lower for cheap ones. That leakage will cascade faster at a higher voltage and break down and heat the electolyte until it pops with a bang.The higher voltage will basically erode away at the various isolations within the IC until something fails internally. The quiecent current will permenantly increase with progressive breakdown, until something internal gets stuck in the wrong state, and the whole thing melts down.

author: dobsonr741
author_rank: Frequent Contributor
timestamp: May 26, 2023, 06:26:04 pm
content: It's a TI part, non-A version. There are TI LV opamp parts with 7V max. The 5.5V max seems to me more like a product categorization/policy question, rather than a direct manufacturing process derived fact.Given it has FET in the output stage, I assume the 10V going haywire voltage coincides with the 10V breakdown of a BiCMOS process.

author: schmitt trigger
author_rank: Super Contributor
timestamp: May 26, 2023, 06:37:14 pm
content: There is a valid reason that semiconductor manufacturers place a note by the absolute maximum ratings table, which reads “operation beyond the maximum ratings is not guaranteed, and may induce a premature and unpredictable failure”. Or words to that effect.Your sample device “worked”, in quotes, and appeared to continue working afterwards, but very likely it has become a “walking wounded” device. No one can predict how it’s performance and/or its service life have been compromised.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: May 27, 2023, 04:24:02 am
content: Quote from: dobsonr741 on May 26, 2023, 05:46:09 pmI see not all xV321 opamps are created equal, many of the ones at lcsc arerail-rail in/out, which may even allow you to lower the operating point ?Most also seem to have 7.5V Maximum ratings.Or, you could pick at part like TLV9101 and get lower Vos and easily run at 6V

author: David Hess
author_rank: Super Contributor
timestamp: May 27, 2023, 10:22:24 am
content: CMOS operational amplifiers like the LMV321 are very intolerant of voltages higher than their absolute maximum ratings and will have drastically shorted operating life. I think this is because of the voltage limitations of the gate oxide which is prone to catastrophic destruction instead of just increased leakage.Old junction isolated bipolar parts like the 741 are limited by other things so 36 volt parts can be graded for operation up to 40 or even 44 volts by monitoring quiescent and input bias current.