is the feedback AC coupled?
Two important parameters to consider:
Common mode input range.
Differential voltage.
Notice that the inputs must be within 0.4Vee and 0.4Vcc
A normal PS is a transformer, rectifier and smoothing caps.
My advice to you is that you turn up your PS slowly and at the same time or that you install a two pole switch.
Two important parameters to consider:
Common mode input range.
Differential voltage.
Notice that the inputs must be within 0.4Vee and 0.4Vcc
A normal PS is a transformer, rectifier and smoothing caps.
My advice to you is that you turn up your PS slowly and at the same time or that you install a two pole switch.
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Yes, and I can't read anywhere that you have the KME49810 on a heatsink which you should have.
The chip is sold in millions of copies (I'll guess) and is verified to work so obviously you have done some mistakes. Nothing wrong with the chip itself if you'll use it as intended. A picture would be good perhaps.
My LME49811 amp locks to the VEE rail if the LME49811 overheats. As soon as the IC cools down for a few seconds, it recovers, though.
It also turns out that if you short the LME49811 heat sink to ground with the heat gun (i.e. short VEE to GND through the LME49811), the LME dies. Grr... No good deed ever goes unpunished, I guess. Another day, another project. I think I still have an LME49811 sample around, so the fix should be pretty easy.
~Tom
Hi Tom,
Thanks for confirming! There surely must be a fault in the design of both LME49811 and LME49810? My circuit does not seem to recover, it just stays locked on VEE even if the chip cools down.
Sorry to hear that you blew up your LME! Probably a good idea to put a silicon washer behind it in future to isolate it from the heatsink
Yes, I have a heatsink.
Can you test the overheating issue in your circuit and let us know if you get the same results that both Tom and I did?
Sorry to hear that you blew up your LME! Probably a good idea to put a silicon washer behind it in future to isolate it from the heatsink
Not really an issue in real life. It's pretty rare I short out the LME heat sink to the main (grounded) heat sink via a heat gun...
It's somewhat lame that the LME bails to the VEE rail, though. That's probably not what you want in an actual design. I'd still argue it's worth a support email to TI. Let me know if anything comes of that.
~Tom
Try putting a diode from each supply to ground so that it's reverse biased during normal operation. This solution helps in many op amp applications when the supplies do not start up simultaneously.
Do you have any insulation between the LME49810 and the heatsink or is the heatsink floating?
Good to hear Tom
Anyone else managed to get their LME's to thermal shutdown WITHOUT locking to VEE?
anyone?
Sorry...
Fully booked with a digital logic volume control att the moment.
A thermo test is still on my to-do-list though...
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