Other Parts Discussed in Thread: TUSB321, TUSB322I, , TPS2552D
Dear *,
i want to build a system that has a USB type C connector and an aux power connector.
The system can be a Device or Host, when we connect to standard PC then it is a device, if we connect a USB-flash key then it is a host.
When the system is a device it can be powered from aux power connector or usb type-c ( always 5V up to 3A per type-c specification), if aux connector is present always prioritize aux connection ( also 5V)
When the system is a host ( usb flash key attached) then the aux connector is always attached and the usb key is supplied with 5V and 1A max.
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so i choose the TUSB321 ic for type-c management:
-with port pin4 we configure that the system is a DRP dual role port
-with current_mode pin3 we says when in DRP-DFP it should advertise max 1A to device (usb flash)
-the OU1,OU2 tells us in DRP-UFP ( when only usb power is consumed, aux connector is not pressent) how much power can give us the host
-the ID pin9 tells us if we are the host or the device
so with ID pin i can control if or device supplies the VBUS or not
do you have a integrated device ( or how to do this) that handle this VBUS switching?
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Because i saw in specification when USB is a host it has to have 120uF on the VBUS, but when it is a device then only 1uF ( in lot of design after the 1uF they us a load switch with SS), and the OTG has a 4.7uF, and i'm not sure the type-c has 10uF?
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there is a block diagram in TUSB322I fro DRP but is missing the device for the USB switch?
Will this work:
I think it is better to power TUSB321AI from 5V SYS all the time.
1) If our device is connected to PC only through USB cable ( needs to be a SINK) and is powered only over USB, then upon attachment of usb cable there is no VBUS and no VDD, the TUSB321AI should present it self ad a SINK, then we get a VBUS and the ID pin is pulled high to 5V VBUS and TPS2275N is enabled and we get 5V SYS and then the TUSB321AI VDD is powered, is that ok?
2) if we connect to PC + external power then the TUSB321AI VDD is powered before TPS2275 is Enabled but this is also ok.
3) if our device has connected only external power then the TUSB321Ai is powered if we connect to PC then happens (2), if we connect a e.g. usb flash drive then the TUSB321 must become Host and pull the ID pin low and enable TPS2552D to source the power to the usb? but one thing here is when only external power is connected and there is no usb cable or device attached then the ID pin is not pulled through 100k i don't know if this is a problem?
Best Regards,
David.
