User's Manual

Table Of Contents
SIM7090G User Manual V1.01
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impedance of 90Ω
USB_DM
10
IO
USB differential data bus (-)
USB_VDDA_3P3
42
PI
Power supply for USB PHY
circuit
EXT_PWR_EN
64
DO
External LDO enable of USB
1.8V power domain
The USB interface is recommended to be reserved for firmware upgrade in customers’ design. The
following figures illustrate reference designs of USB PHY and USB interface.
Figure 14: Reference Design of USB PHY
The reference circuit refers to the following figure.
Figure 15: Reference Design of USB Interface
The following principles should be complied with when design the USB interface, so as to meet USB 2.0
specification.
It is important to route the USB signal traces as differential pairs with total grounding. The
impedance of USB differential trace is 90Ω.
Do not route signal traces under crystals, oscillators, magnetic devices and RF signal traces. It is
important to route the USB differential traces in inner-layer with ground shielding on not only upper
and lower layers but also right and left sides.
Pay attention to the influence of junction capacitance of ESD protection components on USB data