The DC motor 102 includes a rotor 103 induced to rotate in response to a drive current generated by the variable supply voltage (+Vcc). The rotation of the rotor 103 generates a mechanical force that drives a component 108. Going forward, the component 108 will be described in terms of an automotive vehicle window regulator unit 108. It should be appreciated, however, that other components 108 can be driven by the DC motor 102 including, but not limited to, a sliding roof, rear view mirrors, etc. In terms of a window glass regulating unit 108, the DC motor 102 can drive various mechanical components to vary the position of a glass window (e.g., move the window up or down). The input supply voltage (+Vcc) can be actively controlled to vary the voltage level applied to the DC motor 102, thereby adjusting the speed of the rotor 103, and thus the speed at which to move the glass window. A shunt resistor 105 can be connected to the output terminal of the motor 102 to measure AC or DC electrical drive current based on the voltage drop the drive current produces across the resistor 105.

The ripple count circuit 104 includes an amplifier 110, a low pass filter 112, a current differential circuit 114, a bandwidth filter 116, a downstream low pass filter 118, and a comparator circuit 120. The ripple count circuit 104 is configured to filter the drive current based on the rotational speed (ω) of the rotor 103, and to generate a pulsed output signal indicative of the actual rotational speed (ω) and an actual rotational position (θ) of the rotor 103.