Design Approach:
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.
For voltage regulators for motor drivers, I have decided to remove it and control the output voltage through MOSFET via constantly reading the battery voltage at that instance. This removes the very big part of the circuit and reduces the extra thermal and electrical losses. This solution felt very practical according to efficiency and also for manufacturing.
For buck-converter of other circuits, I have chosen a Smart Gate driver IC for the motor driver section by Texas Instruments. This IC has an Integrated LM5008A buck regulator for powering the extra circuit. This also removed the extra components required for buck converters, providing a compact design and reduction in manufacturing cost.
Design the Motor Driver Circuit for making things easy. You can choose any good motor driver IC from Texas Instruments.
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.
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.
High current-carrying copper traces are kept exposed so they can be filled with extra soldering material to make them thicker.
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.
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.
Your communication channel should have proper protection and filters else your communication channel will induce noise.
I have calculated the traces’ and vias’ properties and kept them exactly as wide as required considering safety factors where required. I have also cross-checked these properties with the PCB design toolkit.
Trace width and clearance has been considered and maintained properly to avoid any cross-talk.
At some places, small value resistors are added in series of the path, so the noise affection can be avoided
I have added ferrite beads where necessary.
Track length analysis is done at communication channels and has tuned the channels where needed.
You may or may not choose to have a heatsink.
The components which I have chosen can handle the current without heating a lot.
Still, I have included mounting holes for the heatsink just in case the MOSFETs get heated in practice.
In case, we choose to use a heat sink some modifications to be done during the soldering of Motor terminal pins. Those terminal pins should be soldered from the bottom layer of the PCB.
The battery is not mounted on the board so you need to give a proper connection for the same.
I have used a standard XT-60-M connector for the same.
Even this connector can not be misconnected; still, reverse polarity protection has included using P-Channel MOSFET for extra safety.
Things to take care of are the EMI/EMC effect, power analog-digital grounding, component placement.
Included the Multiple GND vias to reduce the return current path.
I have tried keeping the MOSFET, Inductor, and Capacitor path as small as possible to reduce the EMI/EMC generation.
As we are not doing any sensitive analog process so I skipped the separation of analog-digital grounding. Anyways, It works perfectly without doing it for sure (https://youtu.be/vALt6Sd9vlY)
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.
Extra IC is included at the micro-USB port for ESD protection.
I have added the required decoupling capacitors at STM32 to avoid effect through power lines.
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