User manual

shown on Figure 2-4 for completeness. MPLAB ICD 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.

2.5.4 Debugger Powered

The internal debugger power is limited in two aspects: (1) the voltage range is not as

wide (3-5V); and (2) the amount of current it can supply is limited to 100 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.

Be aware that the target V

DD is sensed by the debugger to allow level translation for

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.

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.

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.

/MCLR

PGC

PGD

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 MPLAB ICD 3 in-circuit debugger system,

as discussed in the following section.