Battery causes device failure

Why would you imagine that? It is not suitable to operate any device @ the MAX ratings, much less above them. By battery, do you mean that you put it in a car and it fried? It is not uncommon to see the voltage constantly above 14.7V in a car. There are other times (google up load dump) that a device in a car may see more than 50V for short periods.

Well, the spec says 15V absolute max and average max is 12.6V so I imagine it's fine. No, it was a car battery... not a car.

I suspect your circuit briefly draws an excessive current pulse. The car battery will happily supply 100 amps. Amps or tens of amps for only microseconds could be enough to destroy a chip.

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You probably have too much resistance in your hook-up wires to draw really large currents; but just a few amps could be enough.

You probably have too much resistance in your hook-up wires to draw really large currents; but just a few amps could be enough.

Looks like some kind of latch-up to me. Probably the bench supply limits the current enough to avoid it. What kind of chip is it that always blows and what's hanging on the other end of it?

Yesterday I designed a half-bridge switcher, another one coming tomorrow. You need to maintain sane start-up conditions. I have current limiting feedback in there, otherwise these thing try really, really hard to get the voltage up at the other end. If the bench supply is a LM317, well, it won't allow it to draw umpteen amps. A car battery does and then ... phsssst ... *BANG*

In cold conditions, try 15.3V nominal, with transients of several hundred volts ;-)

...Jim Thompson

My guess is you have something incorrect in the circuit that is momentarily shorting on start up. The LM317 is only a little pony regulator and would simply fold back. The battery on the other hand how ever, will not give up so easily.

I doubt if initial arching is causing that much damage when connecting the battery how ever, you could try a TVS unidirectional diode across the rails. This will clamp any thing over the selected rating of the diode and kill reverse transients.

When it was cold I usually had zero volts in my Citroen. But ah! I had a stack of four D-cells soldered together. That made the cranking process a lot easier. Chugga, chugga, chugga ... *BANG* ... vroooom. Sometimes I had to wipe the soot off the bumper of the car behind mine. One time the

Back in my automotive electronics days the operating voltage range spec was +4V to +18V, with the requirement to withstand "load dump" AND negative current flow of 20Amps :-(

...Jim Thompson

Most likely it is the initial state that is causing the problem. I guess what happens, and htis is just a guess, is that one or both sides of the hbridge are shorting out and the IC tries to raise the voltage to turn them off but because there is so much current it has an extremely low voltage and it can't turn off the mosfet so it pumps more current trying to turn it off and it can't.

The IC is a Max5063A. These things seem to die left and right when they are around me.... if I just look at them they explode.

(don't understand why, at $4 a pop there can't be any type of protection circuitry)

Well, that is probably it but I'm not sure how to get around it... I can't use a regulator(I can but I don't want to waste power since it's battery powered).

I'm going to try to add some pulldowns hoping that it will work... although not quite sure what resistance to use... to little just wastes power but to much might not solve the problem(I guess I'll have to play around with)... running out of IC's though ;/

I guess what I can do is add the pulldowns, remove the ic's, and then try the battery... if it shorts then it's not the ic's. If it doesn't, then it's the ic's ;)

Look thru the data sheet for some initialization method... everything OFF until Q-point reached.

...Jim Thompson

Post your schematic.

...Jim Thompson

soft start circuit that supply's the bridge.

I was just going to say that. And if taking the IC out means some floating FET gates then all bets are off. That could result in the ultimate kablouie. One where the fire extinguisher has to come on scene ;-)

Well, I never use those high-faluting high-voltage bootstrap things. I use transformers and then regular (a.k.a. cheap) drivers.

The OP talks of 12.6V, which I interpret as the driver power, but wonder what he has for the FET's ???

...Jim Thompson