I think you have been confused by the driver RMS value and the board current limits.
They do not relate to each other directly.
Your driver is a little power supply, which drives the desired current or less (under specific circumstances more) to the motor and consumes power from the mainboard.
So, on paper, without direct measurements of current between the PSU and your board.
You can estimate the real board current in this way (I use an arbitrary stepper online NEMA23 motor data):
- at standstill, for one phase fully energised:
I * V = P = I^2 * R ~= 2.8*2.8 * 0.7 ~= 5.5W - at standstill in middle microstep position:
5.5 * 0.707 * 2 ~= 7W - With motor supply at 24V:
P/V = I ~= 5.5/24 = 0.23A - With motor supply at 48V:
P/V = I ~= 5.5/48 = 0.114A
So, you do have some headroom on your motherboard.
Motors will consume more power than this, maybe 10W at standstill and maybe 30-50W when spinning at high speed, but the principle itself would be the same.
Hope that helps.
(Drivers do, underneath, consume the current from the main power supply, but because of resistance, capacitance, inductance, and how they do that, we can ignore that fact and use the above calculations.)
(How drivers do that: SpreadCycle and StealthChop (an advanced guide))
Btw, I do not see a current limits on the motor power socket in the user manual.