A4988 - what is the decoupling capacitor voltage rating?


I have 2 questions concerning the A4988 Stepper Motor Driver Carrier:

  1. What’s the recommended decoupling capacitor voltage to be connected between VMOT and GND? On the product page, it only shows that a 100 uF bypass capacitor is used but there is no mention anywhere about the voltage rating of the capacitor.

Quote from the product page:

Under the right conditions, these spikes can exceed the 35 V maximum voltage rating for the A4988 and permanently damage the board, even when the motor supply voltage is as low as 12 V. One way to protect the driver from such spikes is to put a large (at least 47 µF) electrolytic capacitor across motor power (VMOT) and ground somewhere close to the board.

  1. I found that in some schematics, there is also a decoupling capacitor connected between VDD and GND. Is this recommended? Why? And what value and what type of decoupling capacitor should be used?

Thanks for the clarifications.


The voltage would depend on your power source at VMOT. To be really safe, I suggest doubling the voltage you use at VMOT.

You should not need a capacitor between VDD and GND unless your VDD supply is noisy or far away.