SoM-A5D36 User Manual
Revision 1.30 © 2015
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3.3.2
Analog Reference
The reference for the analog to digital converter is provided on the SoM with no need to provide and
external reference. The onboard ADC reference is 3.3 Volts and can be switched on and off. The touch
screen uses the ADC pins on the processor so the ADC reference must be enabled for the touch screen
controller to function properly.
3.3.3
Battery Backup
The SoM-A5D36 contains 3 potentially non-volatile memory areas, the eMMC flash, the real-time clock,
and the serial flash of the processor. The flash is always non-volatile, the real-time clock requires a backup
voltage to maintain its data. This backup voltage comes from the VSTBY SoM pin, and should be connected
to 3.3 volts.
The RTC will draw approximately 8 µA when the processor is not powered by the 3.3V supply. Be aware
that the Static current can rise if the temperature increases to 85° C. When the module is powered no
current is drawn from the backup battery supply. If RTC backup is not needed, this can be tied to 3.3V.
The SoM-200GS, as well as other carriers, provide battery backup voltage through a replaceable BR2032,
which is a standard 3V 190mA/H 20MM coin battery that can be picked up from most electronics stores.
3.3.4
Shutdown Logic Pins
The SHDN is a digital output only (0 to 3.3V, pulled up on-module), which is driven by the Shutdown
Controller on the processor.
The WKUP pin has a Maximum input voltage of 3.3V, but cannot exceed VDDBU.
Both of these pins are connected directly to the processor.
