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OPA2140 explosions

Other Parts Discussed in Thread: OPA2134, OPA2140

I have used OPA2140 in a product for the first time now (previously OPA2134) and I am experiencing severe issues. Some of the chips burned or exploded immediately after powering up (replaced them, worked fine), and 2 more have burned after some days, the last one at customers place. I use it as a simple non-inverting unity gain buffer with 100k load and virtual earth mixer with 15k load, so, nothing particularly difficult. There was no input signal when we had problems. Capacitive load is picos. I have never before had OP amps exploding and catching fire and therefore I am very surprised about the issues. The way I used them was not new for me in any way and previously OPA2134 has been fine there. I am in serious trouble, products have been sent all over the world, so please help.  Power supplies are +/- 18V and bypassed with film caps. PCB is standard 2 layer with proper layout. Chip is SOIC.

Has there been a faulty batch of these chips? I can not come up with any other reason. Those chips which work, remain cool.
I bought the chips from Mouser during the Spring.

  • Jonte,

    I have never seen such problem with OPA2140.  However, what you describe is possible if you either incorrectly plug the part into the socket (effective reversing the power supplies) or if the supply voltage you apply exceed even for short time +/-20V absolute maximum rated voltage. Please use scope to look for any excessive transients on the power supply during power up. Other than that, I would look if OPA2140 batch were genuine TI parts.  Please also be aware that OPA2140 input voltage range is limited to 3.5V below positive rail.

  • Marek,

    Thank you for the reply.

    Power supply is very slowly ramping to +/-18V, no problem there as far as I can tell. Parts were oriented the right way. Input was grounded in this case. In the last two cases the equipment was on for a long time before the explosion and worked just fine. Input voltage range should have not been exceeded. BTW, does exceeding the 3.5V to V+ range cause destruction? I suppose the clamping diodes are the ultimate limit?

    How can I know if the part was genuine? I bought them from Mouser in the Spring, so I suppose they are genuine?

    I'm puzzled. And very, very troubled. This is going to cost me a fortune if I have to call the equipment back from all over the world. I hope no more units go up in smoke. When the OP amp catches fire it also destroys the PCB traces underneath. All info and speculations are welcome.

    Kind Regards,

    jonte
  • Jonte,

    Do you use Zener diodes or Transient Voltage Suppresors (TVS) on supply pins to assure quiescent current (IQ) path in case one supply comes on before the other?  Such protection is highly recommended for all circuits - see below.  Without it, with one supply floating even for a short time, quiescent current finds the path for the current to flow thru ESD input protection diode that can typically handle only 10mA or less. 

    I simulated OPA2140 circuit using our macro-model and it shows +/-1.8mA current thru ESD input protection diodes for both, floating Vcc or floating Vee (see below), BUT the actual current might be much higher than simulation shows causing the damage to your circuit.

    You should be able to verify this by measuring the current going in or coming out of the positive input terminal - use e.g. 10 - 100ohm resistor in series with Vin+ and monitor the voltage across it with a scope during power-up.

    Below please see the recommended electrical overstress (EOS) protection scheme.

    For more detailed information about EOS, please view the series on videos under following link:

  • Thank you for the reply.

    No, I don't have any diodes in parallel with power supplies. The powers rise quite nicely in tandem though. But lets assume we have something here.

    You write that the current could be much higher than the quiescent 1,8mA. Why and how much higher?

    Do you know if OPA2140 is more sensitive to this issue than other OP amps? Since like I told, I have never ever had OP amps breaking without obvious reason (obvious for me, that is), let alone catching fire or exploding. The way I see it at the moment, there certainly is some sort of vulnerability not present in other OP amps I have used. Or a faulty batch.


    Thanks in advance.