Datasheet

20-Pin TSSOP and SSOP Evaluation Board User’s Guide
DS51875A-page 14 © 2009 Microchip Technology Inc.
2.3.1 The Hardware
Figure 2-2 and Figure 2-3 shows the component layout of the 20-Pin TSSOP and
SSOP Evaluation Board. This is a four-layer board (3.9" x 2.1" (99.06 mm x
53.34 mm)). There are twenty two connection points/pads that can use either
through-hole or surface-mount connector posts.
The pad labeled VDD is connected to the PCB power plane, while the pad labeled VSS
is connected to the PCB ground plane. All the passive components that are connected
to VDD or VSS are connected to either the power plane or ground plane.
The twenty remaining PCB pads correspond to the device pins (i.e.; pad 1 connects to
pin 1).
Each pad has two passive components associated with them: a pull-up resistor and a
pull-down resistor. The pull-up resistor is always RXU and the pull-down resistor is
RXD. The “X” is a numeric value that corresponds to a particular pad (1 to 8). As an
example, Pad 5’s pull-up resistor is R5U. Capacitor C1 and C2 are the power supply
filtering capacitors. For whichever pin is the device’s VDD, the RxD component
footprint can be used for the device’s bypass capacitor. Table 2-1 describes the
components.
A 6-pin header interface is available that supports the PICkit Serial or the PICmicro
In-Circuit Serial Programming (ICSP) interface. For additional information, refer to
Section 2.4.5 “PICkit Serial or In-Circuit Serial Programming (ICSP) Interface
(Header J1)”.