VNH3SP30 frequency / duty cycle problem

[bjorn]

Posted on September 15, 2008 at 11:25

VNH3SP30 frequency / duty cycle problem

[bjorn]

Posted on May 17, 2011 at 10:15

Hello everybody,

We're doing some tests with the VNH3SP30 motor driver because the bridge we're using at this moment (LMD18200 from National) doesn't do the trick in a new application.

But ..... . I'm having a problem.

The sitiuation is like this : I made a small board with the VNH3SP30 on it, and i'm doing some tests on the testing table with a function generator to deliver the PWM signal.

Here's the problem: At certain frequencies for example 3KHz i can go to 100% duty cycle, but there's double the current needed (only 800mA) then at 80% duty cycle, the driver heats up, and goes into thermal shutdown. The same thing for a low duty cycle.

When i use an extremely low frequency as pwm (100Hz), this doesn't happen.

Is this normal behaviour? Has anybody else encountered this?

Thanks in advance for your help/remarks

Bjorn