Dear support
I bought pololu.com/product/1200 , it is stepper motor size nema17.
I alreaddy have A4988 driver with regulator model pololu.com/product/1183.
According to the specification of motor it is 4v.
The A4988 driver has minimum VMOT. at 8V.
I already read in the FAQS forum , but not clear the about the trimmer.
So…the question is ,
Input to VMOT is 12v. , how to lower to 4v.
Would you guide to me please
thank you
Hello.
It seems you are having trouble understanding the first FAQ on the FAQs tab of our A4988 carrier’s product page. Current limiting drivers like the A4988 limit the current going to the stepper motor. This allows you to use the stepper motor with voltages higher than it is rated for. Turning the potentiometer allows you to set the current limit, and the reference voltage you are measuring at the VREF via is just an indication of what the current limit is set to. It is not the voltage going to the stepper motor. Instructions for setting the current limit are located in the “Current limiting” section of the A4988 carrier product page.
-Derrill
According to your answer…
With the above answer …it look like A4988 can use with motor popolu item#1200.
But the last answer look like it can not. 
Or I have to regulate the 1A 2A 1B 2B output to mach with the motor
Our A4988 stepper motor driver carrier can be used with the #1200 stepper motor. However, since the maximum current the A4988 carrier can handle without additional cooling is only 1A and that stepper motor is rated for 1.2A, you would probably have to set the driver’s current limit to 1A. This would also limit the maximum holding torque the motor could achieve. If you use the A4988 Black Edition instead, you would probably be able to set the current limit to 1.2A and achieve the rated holding torque of the #1200 stepper motor.
-Derrill
Dear Derrill
Thanks for your answer…
Very helpful 
