Digilent 410-297P-KIT - Manual (Page 7)

ChipKIT MX3 Board Reference Manual
Copyright Digilent, Inc. All rights reserved.
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Page 7 of 25
The 5V power bus, VCC5V0 can be powered from one of three sources: 1) The USB5V0 bus when the board is
operating under USB power; 2) The output of the on-board 5V regulator when operating from an external 7V–15V
supply; or 3) Directly from the external supply when operating from a regulated 5V external supply and jumper JP2
is in the BYP position.
Switchover from USB power to external power is done automatically and the external supply will be used if both
are present.
Jumper JP2 is used to route the external power supply voltage through the on-board 5V regulator or directly to the
VCC5V0 bus, bypassing the on-board 5V regulator. Normally, JP2 should be in the REG position. This routes the
external supply through the 5V regulator. Operation from an externally regulated 5V supply is accomplished by
placing the jumper in the BYP position.
The forward drop across the MCP1725 is typically 210mV (350mV max) at 500mA output. With JP2 in the BYP
position, this will allow correct operation of the 3.3V power supply from an input voltage down to 3.5V. This allows
powering the board from batteries and other lower voltage power sources. In this case, the VCC5V0 power bus will
not be powered at 5V.
NOTE: It is extremely important to observe the MCP1725 maximum input voltage rating of 6V when JP2 is in the
BYP position. Applying more than 6V to the external power input with the jumper in the BYP position can damage
the 3.3V regulator and possibly the PIC32 microcontroller as well.
The PIC32 microcontroller is rated to use a maximum of 75mA of current when operating at 80 MHz. This allows up
to 425mA from the VCC3V3 bus and up to 925mA from the VCC5V0 bus to power external devices. The combined
power used by the VCC5V0 bus and the VCC3V3 bus should not exceed 925mA.
The ChipKIT MX3 can provide power to any peripheral modules attached to the Pmod connectors, JA-JE, and to I
2
C
devices connected to the I
2
C daisy chain connector,
J2. Each Pmod connector provides power pins that can be powered from either the switched main power bus,
VCC5V0, or the regulated voltage, VCC3V3, by setting the voltage jumper block to the desired position.
The I
2
C power connector only provides 3.3V from the VCC3V3 bus.
It is also possible to power the ChipKIT MX3 from any one of the Pmod connectors or the I
2
C connector. When
powering the board from a Pmod connector with the power select jumper in the 5V0 position, a voltage applied at
the Pmod connector will power the VCC5V0 bus and be regulated to 3.3V for the VCC3V3 bus. When powering the
board from the I
2
C connector or a Pmod connector with the power select jumper in the 3V3 position, only the
VCC3V3 bus will be powered and the VCC5V0 bus will not be powered.
2.1 RESET
A reset button is at the upper left corner of the board. Pressing this button will reset the PIC32 microcontroller.
3 Pmod™ Connectors
The ChipKIT MX3 has five connectors for connecting Digilent Pmod peripheral modules. The Pmod connectors,
labeled JA–JF, are 2x8 right-angle, female pin header connectors. Each connector has an associated power select
jumper block labeled JPA–JPF.