PWM with Microcontroller (Rabbit BL4S200)

Hey guys,

I'm quite new here... I might need some help to process and correct the signal I'm getting from my microcontroller.
It's a PWM driven by a Sinking Output (~24V), connected to 2 Serial Resistors (15-15 Ohm) and a LED (3.2V @ 700mA)

At 1kHz the signal looks kinda clean, but as the frequency gets higher, the signal goes from square to kinda sinus.



What you see there is the signal passing throught 1 resistor (15 Ohms).

Any idea what kind of approach I should use ? Filter (LC ? RC ?) ? Comparator with Op-Amp ?

[EDIT] The microcontroller I use has 8 High-Current Sinking or Sourcing Ouputs. Up to 2A each. The source I'm using to power everything is a Weidmuller PowerSupply 120W - 24V [/EDIT]
Thanks,

-Baube.

Not quite sure what you're showing here. Is this your PWM output? If you are using PWM, then why is your frequency changing? My guess is your driver is not fast enough to drive nearly an amp at 50 KHz.

What i'm showing is the signal passing through the resistor, to show that the signal is getting shitty as the frequency is getting higher. My goal is to use the microcontroleur to produce a PWM > 50kHz, but the signal is only clean at 1kHz, so It's far from what I need.

The microcontroller says in the spec that it supports PWM on these High-Current ouputs, up to 50kHz.

Does it tell you what the maximum slew rate is? I think what you're seeing is slew-rate limiting.