RE: DRV8701: nFault during driving div. motors

Ladies and gentlemen,
we use the DRV8701P in a prototype design. After some experience with this chip we would like to ask you to answer the following questions: The capacitor listed on page 28 with "bulk" is indicated with min. 10uF. Is there a way to calculate the capacitance of this capacitor? Does the size of the capacity depend on the motor current? The manual does not provide any facts at this point!
Another problem arises from the fact that we have to regulate the speed of a connected DC motor in both directions of travel. The aim is to keep the rotational speed of the engine constant over its entire working range. An external potentiometer gives a voltage to a CPU and the motor connected to the DRV chip must reach a speed proportional to the voltage. We adapt the PWM in each case. For this purpose, we measure the generator voltage of the motor in a gap (no PWM present; IN1=IN2=0) of approx. 0.5 to 1.0ms and transmit it to the motor controller. When the motor is at standstill, a constant voltage of approx. 0.7V is applied between contacts SH1 and SH2! We cannot distinguish this voltage from the generator voltage! The controller erroneously suspects that the motor is rotating. Is there a proposal from TI on how the problem can be solved?
We look forward to hearing from you.
With kind regards
F. Giesen