A4988 current surge

I’m planning to use three Pololu A4988 stepper boards in my project. At the moment just one is fitted and no motor is connected to it.

After I toggle the /reset line to the board, the current consumption of the whole board leaps by 65mA and stays there.
I have Vref set at just 0.19V, although this shouldn’t make any difference with no stepper connected.

Reset is being pulled high by a 10K resistor, my reset pulse is about 1uS long and yes it is going low then high!

the ‘top lip’ test tells me the heat is being dissipated in the chip!

Can anyone duplicate/explain this behaviour?

Dropped a second board in. The current increase remained ~65mA, so I’m assuming the first board has something up.

Now pulling it out :-/

… grr… reflow gun at 450C makes PCB blister, only minor and no tracks damaged, thank goodness!

Three new boards fitted and the increase on reset is now 6mA.

Demand per board is ~ 7mA per board after the reset which is the right sort of value (datasheet says 5mA but that doesn’t include the on-board voltage divider for a start).

What is odd is the boards, must be only taking about 5ma each BEFORE they get reset.

Still not sure why it should change at all but it definitely goes up by 2mA per board after reset?


It sounds like you might have solved your problem. A current increase from the VMOT or VDD supplies is not normal on resetting the chip.