Kauai Labs VMX-pi Reference Manual page 15

VMX-pi Hardware Reference Manual (version 1.10)
microcontroller will continue to function until the VMX-pi input voltage reaches 4V – however these
extremely low voltages are insufficient to support fully-operational scenarios, and can only main
processor life-support. Therefore, the minimum required voltage is 5.75V.
To manage low Input Power voltage situations typically occurring in battery-operated scenarios, when
VMX-pi detects Input Power voltage levels below 5.75V, the External Device power supply output (e.g.,
power supplied to power pins on FlexDIO, HighCurrentDIO, AnalogInput and CommDIO
headers/connectors) is temporarily disabled until the input voltage rises again to approximately 5.85V.
This ensures the full 3A output current remains available to the Raspberry Pi and the VMX-pi
microcontroller.
The system behavior at various Input Power voltage levels is summarized below:
Input Power VMX-pi external
Voltage devices
5.75V and OK
above (at
full 3A load)
Below External device
5.75V Power rail disabled
Below External device
4.75V Power rail disabled
Below 4.5V External device
Power rail disabled
Below 4V External device
Power rail disabled
Raspberry Pi
external USB
devices
OK
OK
Insufficient Power
Insufficient Power
Insufficient Power
Raspberry Pi VMX-pi
Processor Microcontroller
OK OK
OK OK
OK OK
Insufficient Power OK
Insufficient Power Insufficient Power
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