I have a miniPCIe 4G modem card which goes into an adapter card with SIM slot. The adapter card itself can communicate to the motherboard via a UART 7-pin port and via a microUSB port. It can communicate with only one of the connectors without an issue, but as per the modem's datasheet, the modem needs 2 amps during peak usage so connecting it only with the USB port results in power starvation as the port supplies 0.5A at most (modem working fine but during load it freezes).
Since I do not have a UART header on the motherboard, I want to connect the adapter card directly to the PSU 5V molex cable. That would mean splicing the USB cable that goes into the microUSB port, separating the data wires (which should connect the adapter to the motherboard) and the power wire (which should go to the PSU). The ground wire I think it should be connected to both the GND on the USB header on the motherboard and the GND on the molex connector.
This should be easy by itself, however, I want to also connect the +5V pin on the adapter UART port to the PSU, too, because I do not think the microUSB alone can supply 2A without the risk of damage. That way the card will get enough amps through both the UART and USB connectors from the PSU (as per manufacturer's recommendations, it can run on both the UART and USB at the same time), and more importantly, I will be able to get all the necessary power from the same place, allowing me to place a USB relay (on another USB port) between the PSU and the adapter card, so I can disable it through software.
I was told that the adapter card, being simple enough, might cause a conflict between the two the voltage regulators for the two 5V inputs if that voltage is coming from the same place (i.e. the molex 5V connector on the PSU). If that would be the case, I guess the option would be to place a device after the relay (drawing below) that can supply 2 constant 5V outputs so that the two 5V inputs on the card can draw as much power as they need without causing a conflict. I am not sure what type of device I should be looking out for in order to achieve that, or if I should create one myself.
I apologise for the drawing, I do not know how to properly create a schematic as I expected this problem to be rather simple (which it turns out it might not be)
Can I get some recommendations what I need to do in order to make the adapter card fully utilise both 5V inputs (thus drawing as much amps as needed)
Since I do not have a UART header on the motherboard, I want to connect the adapter card directly to the PSU 5V molex cable. That would mean splicing the USB cable that goes into the microUSB port, separating the data wires (which should connect the adapter to the motherboard) and the power wire (which should go to the PSU). The ground wire I think it should be connected to both the GND on the USB header on the motherboard and the GND on the molex connector.
This should be easy by itself, however, I want to also connect the +5V pin on the adapter UART port to the PSU, too, because I do not think the microUSB alone can supply 2A without the risk of damage. That way the card will get enough amps through both the UART and USB connectors from the PSU (as per manufacturer's recommendations, it can run on both the UART and USB at the same time), and more importantly, I will be able to get all the necessary power from the same place, allowing me to place a USB relay (on another USB port) between the PSU and the adapter card, so I can disable it through software.
I was told that the adapter card, being simple enough, might cause a conflict between the two the voltage regulators for the two 5V inputs if that voltage is coming from the same place (i.e. the molex 5V connector on the PSU). If that would be the case, I guess the option would be to place a device after the relay (drawing below) that can supply 2 constant 5V outputs so that the two 5V inputs on the card can draw as much power as they need without causing a conflict. I am not sure what type of device I should be looking out for in order to achieve that, or if I should create one myself.
I apologise for the drawing, I do not know how to properly create a schematic as I expected this problem to be rather simple (which it turns out it might not be)
Can I get some recommendations what I need to do in order to make the adapter card fully utilise both 5V inputs (thus drawing as much amps as needed)
