smooth follow 2d camera runner ios

I have some problem with camera in my 2d runner. I need smooth follow camera, I try this script [2D Camera "Smooth Follow"][1] [1]: http://answers.unity3d.com/questions/29183/2d-camera-smooth-follow.html

But it's still not smoothing. I use function Lerp and one point position. To move my hero I use Character controller (Move). And use rigidbody to set RigidbodyInterpolation.Extrapolate;

 thisTransform.transform.position=Vector3.Lerp(thisTransform.transform.position,cameraTarget.position,Time.deltaTime*2f);

When I try it in PC everything is ok but in device(ipod and Ipad 1) it's not work corectly but in Ipad 2 everything ok; fps=60; Sorry for my bad English