DEMO908QB8 Freescale Semiconductor, DEMO908QB8 Datasheet - Page 12

• Manufacturer Part Number: DEMO908QB8
• Description: BOARD DEMO FOR MC68HC908QB8
• Manufacturer: Freescale Semiconductor
• Type: MCUr

Specifications of DEMO908QB8

• Contents: *
• Processor To Be Evaluated: MC908QB8
• Data Bus Width: 8 bit
• Interface Type: RS-232, USB
• Silicon Manufacturer: Freescale
• Core Architecture: HC08
• Core Sub-architecture: HC08
• Silicon Core Number: MC68HC908
• Silicon Family Name: HC08Q
• Kit Contents: MC68HC908QB8, Cables, Guides
• Rohs Compliant: No
• For Use With/related Products: MC68HC908QB8
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

D E M O 9 0 8 Q B 8
PWR_SEL
Figure 4: PWR_SEL Option Header
Power from the integrated BDM is drawn from the USB bus and is limited to 500 mA. Exces-
sive current drain will violate the USB specification and may result in damage to the host PC or
the target board. At minimum, excessive current drain will cause the host PC to spontaneously
reboot. Power is provided through the integrated BDM to the target board.
The on-board voltage regulator (VR1) accepts power input through a 2.0mm barrel connector
(PWR). Input voltage may range from +6V to +18V. The voltage regulator (VR1) provides a
+5V fixed output limited to 250mA. Over-temperature and over-current limit built into the volt-
age regulator provides protection from excessive stresses. Consider the maximum output cur-
rent limit of VR1 when attempting to power off-board circuitry through connector J1.
VX_EN
The VX_EN option header is a 2-pin jumper that connects / disconnects input J1-1 directly to
the target board +5V voltage rail. J1-3 is hard-wired to the ground plane. Use of this feature
requires a regulated +5V input power source. This power input is decoupled to minimize noise
input but is not regulated. Care should be exercised when using this feature; no protection is
applied on this input and damage to the target board may result if over-driven. Also, do not
attempt to power the target board through this connector while also applying power through the
USB-MON08 or the PWR connector; damage to the board may result.
Power may be sourced to off-board circuitry through the J1 connector. Current limitation of the
USB bus or the on-board regulator must be considered when attempting to source power to
external circuitry. Excessive current drain may damage the target board, the host PC USB
hub, or the on-board regulator. The figure below details the VX_EN header connections.
Figure 5. VX_EN Option Header
NOTE: Do not exceed available current supply from USB-MON08 cable or on-board
NOTE: This header is not installed in default configuration.
VX_EN
1
2
regulator when sourcing power through connector J1 to external circuitry.
Enabled
PWR_SEL
1
ON
2
3
Disabled
OFF
CONFIGURATION
1 – 2: Selects power input from
2 – 3: Selects power input from on-board regulator
12
USB-MON08
M A R C H
1 8 ,
2 0 0 5