Hello everybody. I built a h-bridge with the hip4081a driver, but I'm having a bit of a problem and was hoping you could help me. The hbridge works fine when I connect AHI and BLI to high and ALI and BHI to low. However when I flip it around to change direction it doesn't always work. Sometimes it works, but sometimes for some reason BHO and BLO are both on and cause a short.

BHI BLI AHI ALO
0 1 1 0 -----> works fine
1 0 0 1 -----> doesn't always work

Does anybody know why this happens???

 

Post a schematic.

 

Here is the schematic. Its pretty much the same as the datasheet except for the sense resistors and it has resistors that go to the gate of the mosfet. Not shown in the schematic, but they are there.

 

I got it working with 2 power supplies. Before I was using the same one for the motor and the IC. I used 2 and it works. I think the current demanded from the power supply was making the voltage sag and causing the IC to stop working.

 

I didn't want to start a new thread since its related to the chip. How do you calculate the gate series resistor. Right know I am using a 100 ohm resistor, but I am not using pwm. If I want to use pwm what resistor should I use. Is it as simple as dividing the voltage by the peak current??