User manual

PICkit™ 3 User’s Guide
DS51795A-page 18 © 2009 Microchip Technology Inc.
FIGURE 2-4: STANDARD CONNECTION TARGET CIRCUITRY
2.4.3 Target Powered
In the following descriptions, only three lines are active and relevant to core debugger
operation: pins 1 (V
PP/MCLR), 5 (PGC) and 4 (PGD). Pins 2 (VDD) and 3 (VSS) are
shown on Figure 2-4 for completeness. PICkit 3 has two configurations for powering
the target device: internal debugger and external target power.
The recommended source of power is external and derived from the target application.
In this configuration, target V
DD is sensed by the debugger to allow level translation for
the target low voltage operation. If the debugger does not sense voltage on its V
DD line
(pin 2 of the interface connector), it will not operate.
2.4.4 Debugger Powered
The internal debugger power is limited to 30 mA. This may be of benefit for very small
applications that have the device V
DD separated from the rest of the application circuit
for independent programming, but is not recommended for general usage as it imposes
more current demands from the USB power system derived from the PC.
Not all devices have the AV
DD and AVSS lines, but if they are present on the target
device, all must be connected to the appropriate levels in order for the debugger to
operate. They cannot be left floating.
In general, it is recommended that all V
DD/AVDD and VSS/AVSS lines be connected to
the appropriate levels. Also, devices with a V
CAP line (PIC18FXXJ for example) should
be connected to the appropriate capacitor or level.
VDD
VPP/MCLR
PGC
PGD
V
SS
AVDD
AVSS
2
1
5
4
3
User Reset
4.7K-10K
Interface
Connector
Application
PC Board
Device
Note: The interconnection is very simple. Any problems experienced are often
caused by other connections or components on these critical lines that
interfere with the operation of the PICkit 3 programmer/debugger, as
discussed in the following section.