The DataSheet of CH315 (the first)

5

The upstream contains U3, P3 etc. the up port P3 is used to connect to computer or other USB-Host, U3

etc upstream circuit share power with computer or USB host through P3, at least public ground.

The downstream contains U4, P4 etc, the down port P4 is used to connect to USB-Device, such as USB

keyboard, USB mice, USB Flash Drive, USB data acquisition box, USB controller etc. USB device, U4 etc.

downstream circuit share power with USB device, at least public ground.

There is one group electrical wire between upstream U3 and downstream U4, using common network

cable (category 5 or category 5 unshielded twisted-pair super) connection. The cable included XD+ and XD-

two differential signaling lines and at least one public ground. If there are remaining signal lines, it can also

be used an additional ground wire and power wire.

For the normal eight core cable, please consult to the figure RJ45: two differential signal lines, four

ground wires, two power wires. The power wire can offer +5V source to USB device port, but impact by the

network cable DC resistance of the voltage drop, especially when the USB device draws more current, the

USB device port of the actual supply voltage is usually less than 5V, and even individual USB device may be

unable to work, then need to provide independent power for the downstream.

The capacitance of C11, C12, C14, C15 is from 4700pF to 0.02uF, used to decoupling of internal power.

C13 and C16 is 0.1uF, used to decoupling of power of CH315. C17 is decoupling of the USB device on P4

port. R11 and R12 are used to adjust the internal consult power.

USB port contains P3 and P4, USB bus contain one pair of 5V power wire and one pair of data signal.

Usually, +5V power wire is red, the ground wire is black, D+ signal wire is green, D- signal wire is white.

When designing the PCB, pay much attention to some notes: C11, C12, C13, C14, C15 and C16

connected to the pin as close as possible CH315G, makes sure D+ and D- are parallel, XD+ and XD- are

parallel, and supply ground net or pour copper beside them to decrease the disturbance from outside signal.

7.2. USB signal isolator (following image)

The following USB isolator is composed by two groups CH315H circuit.

LSI# pin directly connect to LSO# pin in CH315H, automatically detect USB speed. In actual, if need

to support certain speed, such as, support low-speed USB keyboard, make LSI# as low-level.