Board Schematics
©
2009 Microchip Technology Inc.
DS51806A-page 24
FIGURE B-1:
PIC18F46J50 FULL-SPEED USB DEMONSTRATION BOARD – PINS
(1,2,3)
1 F
0.1 F
1 F
2.2 F_Tant
0.1 F
56 k
7
100 k
15 k
7
820
7
2 k
7
2 k
7
1.5 k
7
1.5 k
7
0
7
0
7
0
7
0
7
15 k
7
PICkit™ 2 Style
Programming Header
Note 1:
In order to be USB compliant, a USB device that is not purely bus-powered (such as containing a battery or having a
wall cube) should monitor the +5 V
BUS
pin from the USB connector. If the host is not powered or the cable is not
attached, the USB device should not enable the USB module or the D+ (for full speed) or D- (for low speed) bus
pull-up resistor (~1.5 k
Ω
). The
USB_ATTACH
signal can be connected to the microcontroller pin, RC2, through the JP2
jumper header. This signal can be used to monitor V
BUS
.
2:
When laying out a new PCB, providing for ESD protection components (such as U4 and C11) is recommended,
although they may not be necessary in all applications. The microcontroller has some built-in ESD protection, but it
may not be sufficient for all applications depending on board layout and other system level considerations. Having
provisions (solder pads) on the PCB for these extra components adds flexibility for later in the development process.
ESD protection components will likely provide the best performance if they are located as close to the high-voltage
entry point as possible (for example, next to the USB connector). When considering ESD components, it is recom-
mended that selected components add little to no extra resistance in series with the D+ and D- pins, and no more than
a few tens of pF of parasitic capacitance.
3:
Certain pins (RA1, RA5, RB1, RD7 and RB5) perform “double duty”, being connected to more than one pin on the
female headers (ICE module). This is done so that the PIC18F46J50 family device can interface with more of the
pre-existing PICtail™ Daughter Boards and other hardware features on the PIC18 Explorer Board and the
PICDEM™ HPC Explorer board.
