Freescale Semiconductor
11
The on-board voltage regulator (VR1) accepts power input through a 2.1mm barrel connector
(PWR). Input voltage may range from +7V to +18V. The voltage regulator (VR1) provides a
+5V fixed output voltage with current output limited to 250mA. Over-temperature and over-
current limit built into the voltage regulator provides protection from excessive stresses. Do
not exceed the maximum output current limit of VR1 when attempting to power off-board
circuitry through connector J1.
POWER SELECT
Power may be applied to the board through a 2.0mm barrel connector, or through connector
J1. Optionally, power may be routed through connector J1 to supply external circuitry. Power
selection is achieved by using a 4-pos selection header. When attached to the PBMCUSLK,
power is provide by the project board through connector J1.
Use caution when configuring this selection header. Applying power to the module through the
on-board regulator and connector J1 at the same time may cause damage to the module.
PWR_SEL
Figure 3: PWR_SEL Option Header
VDD 4 3
VX 2 1
Source power input from barrel connector PWR.
PWR_SEL
VDD
4
3
VX 2 1
Source power input from connector J1.
PWR_SEL
VDD 4 3
VX 2 1
PWR_SEL
Source power from barrel connector PWR and supply power to external
circuitry connected to J1.
NOTE: Exercise caution when configuring this selection header. Improper configuration may
damage the module.
RESET Switch
The RESET switch provides a method to apply an asynchronous RESET to the MCU. The
RESET switch is connected directly to the RESET* input on the MCU. Pressing the RESET
switch applies a low voltage level to the RESET* input. Pressing the reset switch causes the
reset supervisor at LV1 to assert RESET for 150 ms. A pull-up bias resistor allows normal
MCU operation. Shunt capacitance ensures an adequate input pulse width.
