The DataSheet of CH315 (the first)

6

The upstream contains U1, P1 etc. the up port P1 is used to connect to computer or other USB-Host, U1

etc upstream circuit share power with computer or USB host through P1, at least public ground.

The downstream contains U2, P2 etc, the down port P2 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, U2 etc.

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

There is one group signal isolator circuit between upstream U1 and downstream U2, select magnetic or

optical isolation. The image id optical isolation, the signal isolation is composed by O1+O2 and O3+O4 two

pairs of photic coupler and associated resistance R1~R8, capacitor C7~C10. The type of photic coupler can

select single channel 6N137 or double channels HCPL2631 etc. high-speed photic coupler may require

decoupling capacitors between power pin and ground pin, the figure is not drawn). Used in 12Mbps

full-speed USB signal, need to consider the speed and the speed symmetry, influence on signal slow-moving

and balance, recommended to select the transmission rate is greater than 10Mbit, and adjust the R1/C7,

R2/C8, R5/C9, R6/C10, to optimize the output signal between rising edge and falling edge.

L1 indicates the USB data transfer in progress. The capacitance of C1 and C4 is from 4700pF to 0.02uF,

for Ch315H decoupling the internal power node, C2 and C5 has a capacity of 0.1uF, for Ch315H chip power

supply decoupling.

When designing the PCB, pay much attention to some notes: decoupling capacitors C1, C2, C4 and C5

connect to the pin as close as possible CH315H, makes sure D+ and D- are parallel, and supply ground net or

pour copper beside them to decrease the disturbance from outside signal.