Mosfet driver causing mosfet to heat up

[johnjoejohn]

Anyone use the LT1158CN mosfet bridge driver?? I tried wiring up the same as the example they have and use a small brushed dc motor as load and BOTH of my mosfet gets hot...but the motor runs. The bottom shouldn't get hot because I am only driving the top. The datasheet also said the input pin low turns on bottom and high turns on top but i cannot tell the difference, seems like both are on because both are hot..I double check connection and it looks right..according to their example.

The mosfet I used are beefy, 50A continuous and the dc motor only draws less than 1 amp. Reason for 50A is that I am actually planning on driving bigger motors but now just using the small dc motor for bench testing.

 

[jiripolivka]

Do you use a good heat sink? Did you check the gate voltage to be in line with specifications?

Driving a "beefy"MOSFET means that gate voltage must open its channel. If open, the channel resistance drops to ~10 milliOhms, this is why MOSFETs are preferred as current switches. If not open properly, the channel keeps a higher resistane and its dissipation makes MOSFET hot.

Do you use a protective diode across the channel? A brushed DC motor can kill the MOSFET due to voltage spikes.

 

[Audioguru]

Do you use a protective diode across the channel? A brushed DC motor can kill the MOSFET due to voltage spikes.

A protection diode is connected ACROSS THE MOTOR, not across the Mosfet.