BLDC Motor Driver

Solution and Design approach:

I usually have used Autodesk Eagle but as my college licence is expired and the free version only supports two layered PCB designs, So I have used EasyEDA for now.

Design Approach:

1. Designing the buck converter, selection of the topology and explaining in detail the selection of all your components. You can use an IC for the same too.
1. For voltage regulators for motor drivers, I have decided to remove it and control the output voltage through MOSFET via constantly reading the current battery voltage. This removes the very big part of the circuit and reduces the extra thermal and electrical losses. This solution felt very practical for manufacturing.
2. For buck-converter of other circuits, I have chosen a Smart Gate driver IC for by Texas Instruments. This IC has a Integrated LM5008A buck regulator for powering the extra circuit. This also removed the extra components required for buck converters, providing compact design and reduction in manufacturing cost.
2. Design the Motor Driver Circuit for making things easy. You can choose any good motor driver IC from Texas Instruments.
1. I have chosen Smart Gate Driver IC DRV8350R https://www.ti.com/document-viewer/DRV8350R/datasheet to control the mosfet which comes with plenty of integrated and protection features.
2. I have chosen CSD19536KTT MOSFET https://www.ti.com/document-viewer/CSD19536KTT/datasheet. This MOSFET is capable of handling 272A of current(Theoretically). And can survive 400A of peak current at 100V of supply.
3. High current carrying copper paths are kept exposed so it can be filled with extra soldering material to make them thicker.  
3. As mentioned, your PCB should be detailed with all silkscreen. The maximum number of layers you can go to is 6, also explain the stackup and why you choose the same.
1. I have chosen 4 layers of stackup with Signal, Power, Ground, Signal layers because this PCB can be easily designed with this stack up as I have initially removed unnecessary components by selecting some proper components.  
4. Your communication channel should have proper protection and filters else your communication channel will induce noise.
1. I have added required decoupling capacitors at STM32.
2. I have added ferrite beads where necessary.
3. Track length analysis is done at communication channels and have tuned the channels where needed.
4. Extra IC is included to avoid damage through the micro-USB port.
5. You may or may not choose to have a heatsink.
1. The components which I have chosen can handle the current without heating a lot.
2. Still, I have included mounting holes for the heatsink just in case the MOSFETs get heated in practical.
3. In case, we choose to use heat sink some modifications to be done during soldering of Motor terminal pins. Those terminal pins should be soldered from bottom layer of PCB 
6. Battery is not mounted on the board so you need to give a proper connection for the same.
1. I have used a standard XT-60-M connector for the same. 
7. Things to take care of are the EMI/EMC effect, power analog digital grounding, component placement. 
1. Included the Multiple GND vias to reduce the return current path.
2. I have tried keeping the MOSFET, Inductor and Capacitor path as small as possible to reduce the EMI/EMC generation.
3. As we are not doing any sensitive analog process so I skipped the separation of analog-digital grounding. Anyways, It works perfect without doing it for sure (https://youtu.be/vALt6Sd9vlY)
4. I have tried to keep sections far from each other and tried to keep components as close as possible within these sections to reduce interference between two sections.