Hi Stefan,
The DRV8701P plus external FETs can perform similarly to the DRV8432. There are a few differences, such as the overcurrent monitoring and the overtemperature warning.
- what kind of FET's would I then need?
N-channel MOSFETS are required for both the high side and low side.
A quick list of likely FETs can be found here: http://www.ti.com/lsds/ti/power-management/n-channel-mosfet-transistor-products.page#p267=40;100&p2748=0.82;9.92&p372max=40.3;400&p1961=0.68;9.462&p191=19;20&o4=ACTIVE
The MOSFETs listed below have much lower RDSon than the DRV8432, which will help thermally.
- Is it (if we skip speed control for a seccond) then posible to only use the FETs to change the direction?
Yes, the IN1/IN2 inputs control the direction of the motor.
- How is the speed of the motor then controlled? (is he just switching the FETs at the pwm frequency?)
The IN1/IN2 inputs are PMW'ed to control the motor speed. This is the same as the DRV8432
- Is is also possible to get an armature like speed controller (replace a pot meter with some "logical resistance" or something???)
This is possible. Another method to consider is measuring the BEMF as suggested in the blog: https://e2e.ti.com/blogs_/b/motordrivecontrol/archive/2013/10/25/easy-cruise-control-for-brushed-motors-using-bemf
- what is the difference between a gate driver and a digital output?
The gate driver provide the proper voltages to fully enhance the N-channel MOSFETs. On the low side, the GLx outputs vary from 0V to ~10V. On the high side, the GHx outputs vary from 0V to ~VM + 10V. This is assuming VM > 12V.