Hi,
I'm working on building an SPWM inverter using arduino mini. I wanted to measure both charging and discharging current using a shunt. As shunt is on negative side on the battery, arduino can't directly measure the shunt voltage during charging time. So i built an op-amp circuit with dual rail supply using capacitor pumping circuit for negative rail. here is the schematic diagram. Read VCC here as 14V battery/bench power supply voltage from the inverter circuit, it's not the same as VCC on the inverter diagram. VCC on the inverter circuit is a separate 12V supply.
The OUT is connected to mini's A2 pin. Mini is taking power from 5V regulator output from inverter circuit. I don't have diagram for mini now.

Here is my invereter diagram: As i'm not using U1 anymore, I shorted CurrentSense' with CurrentSense (pin 6 of INV_CTRL header). High side mosfets' drain terminals are shorted externally by heatsink, than 14V supply is applied through the heatsink. VCC is separate a 12V supply from other dc source as I said earlier.

Now the problem is tl084 burned for first time and 555 timer stopped working as well (checked o/p using oscilloscope. no oscillation at pin 3). after replacing both ICs, it worked fine, around 22VDC across tl084, 555 timer oscillating. second time after connecting to inverter cuicuit, and A2 pin on mini, 555 burned cosuming around 220 mA, I didn't checked tl084, didn't try any further attempt. Now I'm wondering why this is failing?I did built and tested this circuit, i.e. op-amp circuit, couple of months ago, and it worked just fine. That time supply for op-amp circuit was 12V from inverter circuit as far i can remeber, and the CurrentSense' - CurrentSense was not shorted. I took input to op-amp circuit from CrrentSense' directly.
Thank you all for reading this thread.

 

I like the large schematics. I can read the values. Good.

I am trying to understand how this works. It appears U3 makes a negativity supply for U1.1.
I have not found "IN".

CurrSense is like this. It is hard to follow the flow of electrons.

I have no idea what kills U1 but the input has no protection. With out knowing what "IN" is I cannot say for certain. I think you should open up U1.1-pin-3 and add a 1k to 10k resistor that limits the current into pin 3. It could be that (at power up or down) the signal going into pin 3 pushes into AGND or VCC and blows up the input protection diodes inside U1.