The SUSPEND pin is a pin prepared to determine whether the CP210x is in suspend state. High during suspend.
Uses of the SUSPEND pin include:

• When the SUSPEND pin is high, the CP210x is in suspend state and other circuits switch to low current mode as well. This is because the current that can be drawn from the USB bus during SUSPEND is specified to be within 2.5mA.

• If the SUSPEND pin is low, determine that the USB host (such as a PC) is active

Such will be considered.
http://community.silabs.com/t5/Interface-Knowledge-Base/CP210x-Suspend-Pins/ta-p/110605http://community.silabs.com/t5/Interface-Knowledge-Base/CP210x-SUSPEND -Pins/ta-p/110909
 
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