Pololu Dual MC33926 - Manual (Page 11)

Using the dual MC33926 motor driver shield with an Arduino (Arduino powered by shield).
It is also possible to power your Arduino directly from the motor shield, as shown in the diagram above, which
eliminates the need for a separate Arduino power supply. When the ARDVIN=VOUT shorting block is in place,
the shield’s reverse-protected input power, VOUT, is connected to the Arduino’s VIN pin. (When power is
connected properly, VOUT is essentially the same as the shield’s VIN.) The Arduino’s power jack must remain
disconnected at all times in this configuration.
Warning: When powering the Arduino from the motor shield, you must never connect a different
power supply to the Arduino’s VIN pin or plug a power supply into the Arduino’s power jack, as doing
so will create a short between the shield’s power supply and the Arduino’s power supply that could
permanently damage both the Arduino and the motor shield. In this case, it is also important that your
shield power supply is an acceptable voltage for your Arduino, so the full shield operating voltage
range of 5 – 28 V probably will not be available. For example, the recommended operating voltage of
the Arduino Uno is 7 – 12 V.
Power Considerations
The shield operates from 5 to 28 V, but it can tolerate transient voltages (shorter than 500 ms in duration) of up
to 40 V, which means it is generally safe to power this board with a 24 V battery. At voltages between 5 and
8 V, the shield performance is derated, and the maximum achievable continuous output current will be decreased
(according to the MC33926 datasheet, H-bridge MOSFET on-resistances might increase by 50% in this “quasi-
functional” performance region). The shield operating voltage range is much wider than the typical Arduino
operating voltage range, so if you are using the shield to power your Arduino, please ensure that your voltage
source is within acceptable limits for your Arduino as well as the shield.
It is important that you use a power source that is capable of delivering the current your motors will require.
For example, alkaline cells are typically poor choices for high-current applications, and you should almost never
Pololu Dual MC33926 Motor Driver Shield User's Guide © 2001–2013 Pololu Corporation
3. Getting Started with an Arduino Page 11 of 24