Hi,

I attach a fragment of a schematic [Fragment.PNG] that I found while searching on the web. I'm trying to decode it. Basically I have four questions (the three red arrows in the diagram):

1- Why is that reference ground there at the source of the parallel FETs? And why that 0.01 ohms/10W resistor at the source of the FETs?
2-Why that RC network in parallel with the motor?
3- Why high side switching is used with N-Channel mosfets? I commonly see high side with P- channel and low side with N-channel.
4- What is the purpose of the 1 Mohm resistor located at the negative side of the bulk capacitors? I know the other side of the resistor is not shown. I didn't attach the whole schematic because it's kind of big and the quality is lost even more. But the other side of the resistor goes to a microprocessor pin named "Vref" like voltage reference.

I attach the whole schematic in PDF, just in case.

 

1. Why is that reference ground there at the source of the parallel FETs? And why that 0.01 ohms/10W resistor at the source of the FETs?
The ground provides the current path for the gate drivers. (notice they are driven by a sub circuit)
The resistor is probably part of the suppression circuit. (just a guess tho)

2-Why that RC network in parallel with the motor?
Suppression (snubber)

3- Why high side switching is used with N-Channel mosfets? I commonly see high side with P- channel and low side with N-channel.
Higher Voltage, higher current…lower Ron at the time the unit was made? Could be a number of reasons.

4- What is the purpose of the 1 Mohm resistor located at the negative side of the bulk capacitors? I know the other side of the resistor is not shown. I didn't attach the whole schematic because it's kind of big and the quality is lost even more. But the other side of the resistor goes to a microprocessor pin named "Vref" like voltage reference.
Probably exactly what you think it is…a voltage reference.

 

1. Why is that reference ground there at the source of the parallel FETs? And why that 0.01 ohms/10W resistor at the source of the FETs?
The ground provides the current path for the gate drivers. (notice they are driven by a sub circuit)
The resistor is probably part of the suppression circuit. (just a guess tho)

2-Why that RC network in parallel with the motor?
Suppression (snubber)

3- Why high side switching is used with N-Channel mosfets? I commonly see high side with P- channel and low side with N-channel.
Higher Voltage, higher current…lower Ron at the time the unit was made? Could be a number of reasons.

4- What is the purpose of the 1 Mohm resistor located at the negative side of the bulk capacitors? I know the other side of the resistor is not shown. I didn't attach the whole schematic because it's kind of big and the quality is lost even more. But the other side of the resistor goes to a microprocessor pin named "Vref" like voltage reference.
Probably exactly what you think it is…a voltage reference.

4- Yes, seems like a voltage reference, but I don't undertand how it is taken from that configuration with a 1 Mohm resistor.