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B-L072Z-LRWAN1 CN11 (USB Conn.) - Device mode

Question asked by Kostas Papouis on May 1, 2018
Latest reply on May 2, 2018 by Kostas Papouis

Hi Everyone,


I would like to ask a question regarding to powering the B-L072Z-LRWAN1 direct from the CN11 USB connector.



The user manual of the B-L072Z-LRWAN1 states the following:
''When the B-L072Z-LRWAN1 board is powered by an external power supply through USB FS connector (CN11), in device mode, do not use a PC as power source if the current consumption is greater than 100 mA, otherwise the PC can be damaged.''


As far as i know a PC's USB2.0 port can provide up to 500mA. On the other hand the maximum current consumption of the B-L072Z-LRWAN1 is 300mA.   Why the datasheet recommends not to source power direct from the PC? My test plan is to power and control the CMWX1ZZABZ-091 direct from the USB port. 

Any help would be highly appreciated.

Thank you.