User manual
Basys MX3™ Board Reference Manual
Copyright Digilent, Inc. All rights reserved.
Other product and company names mentioned may be trademarks of their respective owners.
Page 12 of 56
#pragma config POSCMOD = XT
#pragma config OSCIOFNC = ON
#pragma config FPBDIV = DIV_1
#pragma config FPLLIDIV = DIV_2
#pragma config FPLLMUL = MUL_20
#pragma config FPLLODIV = DIV_1
2 Power Supplies
The Basys MX3 requires a 5V power source to operate. This power source can come from the Programming /
Debugging USB port (J12), the USB-UART (J10), or from an external 5V DC power supply that’s connected to Power
Jack (J11). These three power inputs are connected through Schottky diodes to form the primary input power
network, VIN, which is used to power the onboard regulators and the majority of the onboard peripherals. No
jumper is required to select the input power source. The board will automatically power on while the Power Switch
(SW8) is in the on position and power is present on any of the power inputs.
A power-good LED (LD11), driven by the output of the 3.3V regulator (LMR10515), indicates that the board is
receiving power and that the onboard supplies are functioning as expected. An overview of the Basys MX3 power
circuit is shown in Fig 2.1.
Micro-USB
Port (J10)
UART
Micro-USB
Port (J12)
DEBUG
Power
Jack
(J11)
5V Input
Power On
LED (LD11)
VBAR
VCC3V3
J2
1
DBG_5V0
FT_5V0
J1
1
Servo Headers
JP1
1
Terminal
Block
(J5)
VEXT (0 – 11V)
Power
Switch
(SW8)
IC10: LMR10515
1.5AVIN
EN
+
-
ON/OFF
IC7: DRV8835
Motor
Driver
VM
VU5V0
IC11: LP2985IM5-3.3
VOUTVIN
ON
VIN
PWR_ON
VIN
DBG3V3
Figure 2.1. Power supply circuit.
The USB port(s) can deliver enough power for most designs; however, a few demanding applications, including any
that drive multiple peripheral boards, may require more power than a USB port can provide. In these instances, an
external power supply can be used. Due to their high current demands, motors and servos cannot be powered
through either of the USB ports, and may only be powered through an external supply.