The regulator can be disabled by driving the regulator shutdown pin,
SHDN
, high.
Power selection
The Zumo 32U4 main board’s power selection circuit uses the
TPS2113A power multiplexer
[https://www.pololu.com/product/2596]
from Texas Instruments to choose whether its 5 V logic supply (designated
5V
) is sourced from USB or the batteries via the regulator, enabling the robot to safely and seamlessly transition
between the two sources. The TPS2113A is configured to select regulated battery power (VREG) unless the
regulator output falls below about 4.5 V. If this happens, it will select the higher of the two sources, which will
typically be the USB 5 V bus voltage if the Zumo is connected to USB.
Consequently, when the Zumo 32U4 is connected to a computer via USB, it will receive 5 V logic power even
when the power switch is off. This can be useful if you want to upload or test a program without drawing power
from the batteries and without operating the motors. It is safe to have USB connected and battery power switched
on at the same time.
The currently selected source is indicated by the
STAT
pin; this pin is an open-drain output that is low
if the batteries are selected and high-impedance if the USB supply is selected. The current limit of the
TPS2113A is set to about 1.9 A. For more information about the power multiplexer, see the
TPS2113A
datasheet
[https://www.pololu.com/file/download/tps2113a.pdf?file_id=0J771]
(1MB pdf).
3.3V regulator
The main board also has 3.3 V linear regulator. The inertial sensors draw power from the 3.3 V line; the
remainder (up to a few hundred milliamps) is available for powering external circuits or devices.
Alternative power sources
For users who want to experiment with alternative power sources like lithium batteries, the Zumo 32U4 can
accept a battery input voltage from
2.7 V to 10 V
. You can raise the maximum allowable voltage to the motor
drivers’ limit of 11 V by disconnecting or modifying the battery voltage divider.
We do not recommend using a 3-cell lithium battery to power the Zumo 32U4. Even though such
a battery is usually specified with a nominal voltage of 11.1 V, it can measure well over 12 V
when fully charged.
Adding a power switch
You can add your own power switch to the Zumo 32U4 using the
PSW
pin. When it is in the on position, your
switch should connect PSW to GND. In that case, VBAT will receive power when either your switch or the main
board switch are on.
3.9. Expansion areas
The top expansion areas on the Zumo 32U4 main board (in two 2×13 groups of pins near the left and right edges)
break out all of the ATmega32U4 microcontroller’s general-purpose I/O lines and provide access to various
power inputs and outputs. Some of these pins are also broken out in the front expansion area, where the front
sensor array connects. The following diagrams identify the locations of these pins and the hardware associated
with them.
Pololu Zumo 32U4 Robot User’s Guide
© 2001–2015 Pololu Corporation
3. The Zumo 32U4 in detail
Page 23 of 76