Table 26: LM940 Hardware Interfaces
6.6.1. USB Interface
The LM940 module includes super-speed USB3.0 with high-speed USB2.0 backward
compatibility. It is compliant with Universal Serial Bus Specification, Revision 3.0 and can
be used for control and data transfers as well as for diagnostic monitoring and firmware
update.
The USB port is typically the main interface between the LM940 module and OEM
hardware.
USB 3.0 needs capacitors on the TX lines in both directions for AC coupling. To interface
USB3.0 with an application board of customer, 0.1uF capacitors should be installed on
USB_SS_RX_P/M lines of the LM940. There are already capacitors on USB_SS_TX_P/M
lines inside LM940 module.
The suggested USB interface connection is the following:
Figure 13: Connection for USB Interface
Note: The USB signal traces must be routed carefully. Minimize trace
lengths, number of vias, and capacitive loading. The impedance value
should be as close as possible to 90 Ohms differential.
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