I'm working on a MOSFET switching circuit that will be used in light- and heavy-duty automotive applications. As such, driving power will come from either a "normal" 12V automobile system or a 24V system commonly used in heavy-duty vehicles.
I'm using two LM2940 LDR's (a 5V and a 12V) to power the IC's in the circuit. Only the drain of the MOSFET will be connected straight to incoming power.
Power comes in to the high power board from the low side of the driven load (I will not know what the driven load is), and then connects directly to vehicle ground and will be limited (via PWM duty cycle) to 30A (currently) or 50-60A (in the future).
I want this to be a very robust system and have a couple issues that I'm struggling with being new to electronics.
1) It seems, in theory, like a TVS (I've been looking at the Vishay SM8A27) across the input power and ground would do just about everything I need. Only power from the LM2940 gets to the control circuit, and it has some of its own built-in protection as well. Besides wrong polarity, high transient voltages, and high transient currents, what do I need to be concerned about? Also, would a TVS like the one mentioned above adequately protect from these concerns?
2) Anticipating that this will often be driving a motor of some sort, and not having the ability to put a flyback diode across the motor, what (else) could I do in my circuit to manage those transients, or is the TVS enough?
Thanks for your help, sorry I can't post schematics but I hope I've been clear.
I'm using two LM2940 LDR's (a 5V and a 12V) to power the IC's in the circuit. Only the drain of the MOSFET will be connected straight to incoming power.
Power comes in to the high power board from the low side of the driven load (I will not know what the driven load is), and then connects directly to vehicle ground and will be limited (via PWM duty cycle) to 30A (currently) or 50-60A (in the future).
I want this to be a very robust system and have a couple issues that I'm struggling with being new to electronics.
1) It seems, in theory, like a TVS (I've been looking at the Vishay SM8A27) across the input power and ground would do just about everything I need. Only power from the LM2940 gets to the control circuit, and it has some of its own built-in protection as well. Besides wrong polarity, high transient voltages, and high transient currents, what do I need to be concerned about? Also, would a TVS like the one mentioned above adequately protect from these concerns?
2) Anticipating that this will often be driving a motor of some sort, and not having the ability to put a flyback diode across the motor, what (else) could I do in my circuit to manage those transients, or is the TVS enough?
Thanks for your help, sorry I can't post schematics but I hope I've been clear.