4.4 Low-Power Measurement

Power to the PIC18F56Q71 is connected from the on-board power supply and VTG pin through a 100 mil pin-header marked with “POWER” in silkscreen (J101). To measure the power consumption of the PIC18F56Q71 and other peripherals connected to the board, cut the Target Power strap and connect an ammeter over the strap.

To measure the lowest possible power consumption, follow these steps:
  1. Cut the POWER strap with a sharp tool.
  2. Solder a 1x2 100 mil pin-header in the footprint.
  3. Connect an ammeter to the pin header.
  4. Write firmware that:
    1. Tri-states any I/O connected to the on-board debugger.
    2. Sets the microcontroller in its lowest Power sleep mode.
  5. Program the firmware into the PIC18F56Q71.
Figure 4-7. Target Power Strap
Tip: A 100-mil pin-header can be soldered into the Target Power strap (J101) footprint for a simple connection of an ammeter. Place a jumper cap on the pin-header once the ammeter is no longer needed.
Info: The on-board level shifters will draw a small amount of current even when not used. A maximum of 2 µA can be drawn from each I/O pin connected to a level shifter. Therefore, the worst case maximum for the five on-board level shifters is 10 μA.. Keep any I/O pin connected to a level shifter in the tri-state to prevent leakage. All I/Os connected to the on-board debugger are listed in 5.2.4.1 On-Board Debugger Connections. The on-board level shifters can be completely disconnected to prevent leakage, as described in 8.4 Disconnecting the On-Board Debugger.