Greetings. We would like to use MP4245 to power not the USB port but internal board circuitry PLUS a USB port. The current limit for the port will be implemented externally.
In that case is it correct to split grounds and place the current sence resistor between system ground (which is electrically identical to USB port ground) and the power ground? The datasheet implies that the CS resistor should be connected between the USB ground pin and PGND as if the converter should only power a USB port and nothing else.
Thank you.
Hi arj1939,
Thank you for contacting the MPS Forum. What is the USB port you are using, is this a controller? The easiest way to implement this would be to just follow the MP4245 + PD Controller schematic from the datasheet. This would sense both the current to the USB bus and internal board circuitry, but this should be acceptable I believe. This would just be sensing your total output to both devices.
I believe splitting grounds and placing the current sense resistor between the system and power grounds is just disabling the sense of the device, but you may want to send diagram/schematic of this if I am misinterpreting what you are saying.
Thanks,
Brendan Schoemehl
Field Applications Engineer
Monolithic Power Systems | MPS Now