New to electronics and trying to understand how to read and interpret data sheets for MCUs, particularly w.r.t. voltage and current supply.
I'm trying to understand the voltage/current specifications for this Atmel evaluation board, as it has seemingly contradictory verbiage within its own user guide.
Certain verbiage suggests the board requires a 5V power supply:
From §3.3 Power Sources:
"External Power: 5V ±2% (±100mV) for USB host operation. 4.3V to 5.5V if USB host operation is not required."
From §3.4.2 Xplained Pro Power Header:
"The power header can be used to connect external power to the SAM R21 Xplained Pro kit. The kit will automatically detect and switch to any external power if supplied. The power header can also be used as supply for external peripherals or extension boards. Care must be taken not to exceed the total current limitation of the on-board regulator when using the 3.3V pin."
To me, these two sections contradict each other. One one hand its saying to operate the board around 5V, but then elsewhere it says never to bring the board higher than 33V. Also, in that same table in section 3.3, there's a column about current requirements that also seems to contradict itself. On one hand it says:
"Recommended minimum is 1A to be able to provide enough current for connected USB devices and the board itself. Recommended maximum is 2A due to the input protection maximum current specification."
Which to me tells me the board wants 1A - 2A of current at all times. But then it goes on to say that the USB devices require 0.5A (which I understand is the USB spec).
I am trying to understand:
- What voltage/current the board itself recommends/wants to power itself without issue; and
- What voltage/current is supplied to and expected from the GPIO pins (so I know what voltage/current compatibilities need to exist with any peripheral I hook up to them)
Thanks for any and all clarifications here!