a4983 questions

Was wondering if someone could alleviate some concerns I have, in using the A4983 Carrier Boards, by answering a few questions, I have.

  1. Does the A4983 limit the current to the stepper to its maximum 2 amp limit? The reason I ask is that I have 2.9vdc 1.4a bipolar motors. If I was to run these at the lowest voltage available, from the A4983, which is 8volts this results in aprox. 4 amps. Following the carrier’s advice, about the potentiometer, states that you can measure the current through the motors without jogging the step input and limit the current that way; which leads me to my next question.

  2. Doesn’t the current, to the stepper motor, instantly flow when powered and that is why you have the holding torque? So would this be limited to 2 amps before I adjust the potentiometer?

  3. Why does the cutsheet state that the chip is limited to 2 amps and then go on to say that “the chip itself will overheat at currents lower than that” and then also say that anything above 1 amp needs a heatsink. I just don’t understand why the chip itself will overheat when I lower the current.

Thank you in advance for your time and help,


  1. The driver limits to what you set on the pot; it’s up to you to set something reasonable.

  2. Current does not flow instantly, in the sense that it does not instantly reach the ultimate limit. When you apply a voltage to an inductor, the current will go gradually the same way voltage will go up gradually when you apply power to a capacitor. The stepper motor effectively regulates the current in your coil, so even though it would want to go to 4A, the power will get turned off once you’re past the set point and then turned back on once you’re under it. There’s a detailed drawing of what the current does on page 9 of the datasheet.

  3. There are multiple limits on performance, and you will always be limited by the lowest one. The chip can do up to 2A, so that is one limit: you’re just not going to get more than that. Another limit is the temperature: it can’t get past 150 C. Without extra effort (e.g. adding heat sinks), you will hit that limit at around 1A. So, we’re not saying the chip will not overheat at 2A and will at 1A; we’re saying that overheating will become an issue around 1A, and you absolutely will not get past 2A.

- Jan


Thanks for the reply. I realized the third item was me overthinking it, right after I posted. I found that the a4983 doesn’t limit the current, just like you mentioned. I noticed that I didn’t have to worry about the current due to the chip overheating at 300 mA. After experimenting with motor voltages between 8 - 24vdc and monitoring the vref pin, I calculated that I could only deliver 300 mA before the overtemp limit kicked in.

I’ll turn my vmot back down to 8vdc, cut a heatsink down to size, and then maybe I’ll get these motors moving and worry about the current limit then.

Are these chips meant to control very small steppers? Is anyone driving nema 23’s with these? I’m looking for a superior alternative to the l297/l298 combo.

You should definitely be able to get quite a bit more than 300 mA. It’s possible that your measurement or calculation has some error in it since the current is usually not constant.

“Very small” is relative. You can see the motors we carry, which generally work nicely with this driver, and they are quite a bit smaller than NEMA 23. However, there are stepper motors way smaller than that. The Allegro driver should be pretty close, output-wise, to the L298, but it’s pretty easy to add a huge heat sink to the L298, so you might be thinking of a heat sinked unit in your assessment of the L298. The L298 also requires external diodes, which distributes the heat dissipation even more. However, if you have a good L298 setup with heat sink and external diodes, and your concern is about maximum power output, not things like size, performance, and efficiency, the A4983 is probably not superior to the L298.

- Jan


Something was wrong with my first board. Soldered up my second one and everything worked fine. These things are amazing.