I've reduced my H-Bridge down to a single N-Channel Mosfet(IRF540) driving a small brushed DC motor for testing purposes. Drain is to +12vdc, source to motor,motor to gnd.
According to the scope, the bootstap circuit is providing a goodlooking 22vdc pwm (about 2k hz)to the gate. Should be fully on. My question is this, if I replace the motor with a 10ohm,10watt resistor, I can crank the pwm up to 100%(12vdc) and observe a steady 1.13amps while the fet doesn't even get warm. If I put the motor back in place of the resistor, I can only crank it up tp .50 amps and the fet gets too hot to touch. I'm assuming the inductance of the motor has something to do with that but I don't know how to deal with it.
One other question, how many amps should a properly driven , high side, not heatsinked fet deliver before getting to warm to touch(about 135F).
Thanks for any help.
According to the scope, the bootstap circuit is providing a goodlooking 22vdc pwm (about 2k hz)to the gate. Should be fully on. My question is this, if I replace the motor with a 10ohm,10watt resistor, I can crank the pwm up to 100%(12vdc) and observe a steady 1.13amps while the fet doesn't even get warm. If I put the motor back in place of the resistor, I can only crank it up tp .50 amps and the fet gets too hot to touch. I'm assuming the inductance of the motor has something to do with that but I don't know how to deal with it.
One other question, how many amps should a properly driven , high side, not heatsinked fet deliver before getting to warm to touch(about 135F).
Thanks for any help.