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I am using a stepper motor of the following rating: Voltage : 3 -5V Current 2.5A/ phase. When two wires of the coil areconnected with a dc power supply at 5V and ground, the motor takes about 2.5A.

I want to use a a stepper motor driver and the selected one is DRV8424 fro Texas Instruments(link of the datasheet attached). https://www.ti.com/lit/ds/symlink/drv8424.pdf

The current rating shows 2.5A as the full scale output current. Is it okay to use this for the motor?

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  • \$\begingroup\$ I think TI DRV 8424/25 and DRV8824/25 can handle 2.5A/coil. But have you considered cheapy modules such as this one: AliExpress DRV8825 Stepper Motor Driver Module US $ 1.53 aliexpress.com/i/32533968646.html. \$\endgroup\$ – tlfong01 Jan 18 at 9:05
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    \$\begingroup\$ It should function, but if you want it to be nice, give it more breathing room in that current spec. The chip may need to dissipate heat, and that can change with motor conditions. Also FYI the voltage rating of the motor is at DC, which is relevant in case you want max combination of speed and torque, for which you would need higher supply voltage, which again increases thermal load \$\endgroup\$ – Pete W Jan 18 at 9:41
  • \$\begingroup\$ @Pete, Ah yes, the cheap module goes with a cheap heat sink, or you can replace the cheap stuff with something better. \$\endgroup\$ – tlfong01 Jan 18 at 9:55
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Probably they will, if you check the "Absolute maximum ratings" in the product datasheet you see that the output currents are stated as "internally limited". Just be careful during the PCB design phase, 2.5A will generate quite a lot of heat. Be sure to design a proper copper plane to dissipate it, make sure to have large enough traces (planes) to carry current to the IC. Consider also adding an external heatsink on top of the chip, even if it has a plastic package it is better than nothing.

Anyway I am pretty sure 2.5A refers to the stall current (maximum current drawn, max torque, motor stalled), so you will probably stay under this current during normal operation of the motor.

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Note that "rating" (fake rating) voltage 5V of the motor means that if you connect this voltage on the coil, the current will be rated current - 2.5A. This rating is intended for driving the motor by using simple transistor switching, without chopper.

If you will spin this motor very slow, then it will be OK. If you intend to spin it faster, you do need much higher voltage due to BEMF of the motor and of course using a motor driver IC.

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