Microchip Technology XLP User Manual page 25

3.2.3.2
The green power LED (D9) illuminates when power is supplied from either the external
9V power supply or the USB connector.
3.2.3.3
The LDO regulator (Q1) is adjustable, and can support a wide voltage range for both
board component and microcontrollers. It can be configured between 1.8V to 5.5V by
changing the values of the voltage divider formed by R28 and R29. Typical values are
listed in
provided in
the LDO is configured to supply 3.3V.
The typical drop of the LDO is approximately 1.75V. Ensure the fixed power supply or
USB supply voltage exceeds the desired microcontroller voltage by at least this amount.
Note:
The performance of the MCP9700 and the LEDs is diminished at 1.8V operation. If
RS-232 communication is needed at 1.8V, populate the LTC2801 and associated
components. See
TABLE 3-2:
3.2.3.4
The XLP 16-bit board supports multiple regulator configurations for PIC24F devices
with an internal voltage regulator. A slider switch (S4) allows the user to configure the
board for either J-series or K-series Flash devices. With switch, S4, in the "PIC24FJ"
position, the microcontroller's internal voltage regulator is enabled by connecting a
pull-down resistor to the DISVREG pin and a 10 µF capacitor to the V
For PIC24F J-series devices, additional power savings can be achieved by disabling
the regulator. Three methods are supported by making several component changes to
the "PIC24F VREG" section of the PCB:
• Separate power supply for V
• V
DDCORE
• V
DDCORE
The required component changes are summarized in
TABLE 3-3:
J-Series Regulator
Split V
Same V
V
DDCORE
Legend: NP = Not Populated; P = Populated
 2009-2015 Microchip Technology Inc.
XLP 16-Bit Development Board Hardware
POWER LED
ADJUSTABLE SUPPLY VOLTAGES
Table 3-2. The equation relating the resistor values to the target V
Figure A-3 of Appendix A. "Development Kit
Always verify that the voltage selected on the LDO meets the V
specification of the installed PIC24F device.
Section 3.2.14 "RS-232 Serial Port Options"
RESISTOR VALUES FOR R28/R29 VOLTAGE DIVIDER
Component
R28 150
R29 450
ON-CHIP REGULATOR CONFIGURATIONS (PIC24F J-SERIES)
and V connected together
DD
connected through a zener diode to V
COMPONENT CHANGES FOR DISABLING ON-CHIP
REGULATOR
Option
R3
and V NP
DD DDCORE
and V 0
DD DDCORE
Zener Diode NP
Target V
1.8V 3.3V
120
200
and V
DD DDCORE
DD
Table
Component Placement and Value
R4 R5
NP 1 k
is
DD
Schematics". As shipped,
DD
for more information.
DD
5.0V
75
33
pin.
CAP
3-3.
V Test
CAP
C4 D6
Point
NP V
DDCORE
NP NP N/C
P N/C
DS50001873C-page 25