EHS5 module, VUSB/VBUS is Valid - Power Down Mode/Power OFF (No VBAT) | Thales IoT Developer Community
June 6, 2014 - 1:40am, 5316 views
Condition:
VUSB_IN pin of EHS5 module is connected to USB Host connector (Host/Charger) VBUS pin through 10K Series Resistor. When VUSB_IN pin reads a valid VBUS voltage range and there is NO Activity on USB Bus (USB charger connectivity / Enumeration Failure)
Questions:
1) Is it possible to put the module in to Power down mode?
2) Is it safe to remove Power (VBAT) to power OFF the modules?
Thanks,
Jun 6 2014 - 1:54pm
Hello,
are you implementing some kind of non typical application? It is not necessary to connect VBUS_IN through an extra resistor. According to chapter 2.1.3 of Hardware Interface Description you can directly connect USB to the module.
Answers:
1) Yes, but you need to take into consideration limitations described in chapter 3.3 of Hardware Interface Description.
2) It is not recommended to power off the module this way as it may damage flash. Always use AT^SMSO for disabling.
Regards
Jedrzej
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Jun 6 2014 - 8:50pm
Thanks for your reply,
Regarding the VBUS Connectivity through a Series resistor is to limit the current in scenario where VBUS will be @ 5V and NO Battery voltage applied to the module. 10K is chosen as series resistor because the VBUS detection current requirement is 100uA (from Module Spec)
Regarding my 2nd Question, you are right.The module will be shutdown using AT command first and as a final step, to save maximum power VBAT shall be disconnected. During this scenario, having a VBUS valid voltage (USB charger) through 10K resistor to Module is OK?
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Jun 9 2014 - 4:10pm
Regarding this statement "VBUS detection current requirement is 100uA"
There is following note in chapter 2.1.2 "Signal Properties" regarding VUSB_IN
"VImin = 3V
VImax = 5.25V
Active and suspend current:
Imax < 100μA"
This means that maximum current the module will draw with supplied voltage from range 3V - 5.25V will be lower than 100μA. It shall work with the resistor installed, but it's not needed.
VUSB_IN can be connected when VBAT disconnected.
You can disconnect VBAT after disabling the module with AT^SMSO.
Regards
Jedrzej
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Jun 9 2014 - 8:05pm
Thanks for all your answers and clarifications
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