DRV8833 delivers power to Arduino

Hello everyone,

I have a DRV8833, which is connected to an Arduino Nano as follow:
GND->GND
BI1->D3
BI2->D5
AI1->D6
AI2->D11
SLP->D2
BO1, BO2 -> motor 1
AO1, BO2 -> MOTOR 2
GND and VIN are connected to a 6V battery.

However, when I turn the 6V battery on, the Arduino gets power (4,5V coming in VIN). This also happens when I spin one of the motors very fast.

Why is this happening, because the 6V battery is not connected to the Arduino?
Thanks in advance.

Thank you in advance.

It's from the protection diodes on the AVR pins. For details please look at the ATMEL datasheet.