H-bridge fire ?

[gstavrev]

Hi,
I just placed a quadruple half h bridge driver in my circuit. I am running it with a pic18, and a TI H - bridge.

This is the data sheet for the driver: https://www.electro-tech-online.com/custompdfs/2008/09/sn754410.pdf

Anyhow, I tried it first with the 5V off the microcontroller to power a small hobby motor, and it worked fine. It was reversing fine as well. I then tried to use a gear motor that I want with same 5 volts and that was fine as well. I have 4 of these motors that need to be driven in pairs. They are 12V motors so I have a 12V Ni-MH battery at 2300mAh. I have tried it with no chips and it drives the motors fine.

I then hook up the 12V batter to the designated pin on the driver and the other to the common ground for the microcontroller and everything, turn on the microcontroller and the driver starts smoking. Looking at the data sheet, the driver should be able to handle 2A at peak and 1.1A steady. When I connect the motor the the battery by it self, I read 70mA of current draw.

The other half (2/4) of the driver still work correctly. I have a spare but just one.

I was wondering what I am doing wrong? Maybe I connected the battery wrong, but I would your advice before I try again.

Thanks

 

[gstavrev]

I am making some progress to finding the problem. I have found this little tutorial that is very similar to my setting:

**broken link removed**

I tried not connecting a motor and not providing anything to the enable pin. The chip gets hot. I run the regular 5V from the microcontroller and it heats up slowly. I use a 9V and it heats up faster, and with 12V its almost instantly. Could something be wrong with the bridge?

I also noticed that when the higher voltage is not supplied to the chip on pin VCC2 it doesn't heat up. And when I change the Vcc1 with Vcc2 it doesn't heat up. Maybe I have the chip upside down? (this will be ridiculous).

Thanks.

 

[3v0]

Unless you post schematic and maybe code all anyone could do is guess about what you are doing wrong.

But first check to ensure that what you have wired is what you think you have etc. Check what you know how to.