Digilent 410-295P-KIT - Manual (Page 8)

ChipKIT Pro MX4 Reference Manual
Copyright Digilent, Inc. All rights reserved.
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Page 8 of 37
If the licensed debugger is connected to an active USB port, it enumerates with the host computer and once it has
been successfully enumerated, it turns on the main board power supply by driving the PWR_ON signal high.
If the licensed debugger is not connected to an active USB port, the PWR_ON signal is ignored and board power is
turned on immediately by the power switch via transistor Q4.
The main board power supply is a switch mode voltage regulator implemented using a Microchip MCP16301
switch mode step-down regulator. This regulator provides 3.3V at up to 600 mA with approximately 96%
efficiency. This powers the main board regulated power bus BRD_3V3
There are three connectors on ChipKIT Pro MX4 for connecting an external power supply: J13, J14, and J18.
The barrel connector, J13, is useful for desktop development and testing where using USB or battery power is not
suitable. J13 is the connector used by the AC adapter optionally available from Digilent, or other sources. J13 is a
2.5mm x 5.5mm coaxial connector wired with the center terminal as the positive voltage.
Connector J14 is a two-pin male header that provides easy battery or battery-pack connection. Digilent has both
two-cell and four-cell AA battery holders with two pin connectors available for connection to J14.
Connector J18 is a screw terminal connector for an alternative power supply connection for use with higher
current battery packs, bench supplies or other power sources where use of a hard wired power supply is desirable.
Connectors J13, J14, and J18 are wired in parallel and connect to the “External Power” position on the Power
Select jumper block J12. A shorting block should be placed on the “EXT” position of J12 when using this option for
board power. Only one of these three power connectors should be used at a time. If multiple power supplies are
connected simultaneously, damage to the board or the power supplies may occur.
When using an external power supply, ensure that the polarity is not reversed as the board is not protected from
reverse polarity on the power supply and will be damaged.
The ChipKIT Pro MX4 has a second screw terminal connector, J5 that supplies power to the servo power bus, VS, to
power the RC hobby servo connectors. This allows servos to be powered from a separate power supply than the
one powering the electronics on the ChipKIT Pro MX4. This can be useful when using servos that draw large
amounts of power.
Jumper JP1 can be used to connect the ChipKIT Pro MX4 unregulated power bus BRD_VU to the servo power bus,
VS. When no shorting block is installed on JP1, the BRD_VU and VS busses are separate. When a shorting block is
on JP1, the two busses are joined and the BRD_VU bus can be powered in any of the previously indicated ways, or
from connector J5.
The ChipKIT Pro MX4 can provide power to any peripheral modules attached to the Pmod connectors and to I
2
C
devices powered from the I
2
C daisy chain connectors, J2 and J6. Each Pmod connector provides power pins that
can be powered by either unregulated voltage, BRD_VU, or regulated voltage, BRD_3V3, by setting the voltage
jumper block to the desired position. The I
2
C power connectors only provide regulated voltage, BRD_3V3.
The PIC32 microcontroller and on-board I/O devices operate at a supply voltage of 3.3V provided by the BRD_3V3
bus. The PIC32 microcontroller will use approximately 55mA when running at 80MHz. The other circuitry on the
board will use approximately 10mA. The remaining current is available to provide power to attached Pmod and I
2
C
devices.