Block Diagram
http://www.motorola.com/computer/literature
3-23
3
Fuses and Polyswitches (Resettable Fuses)
The MCP750HA provides current limit protection for the power rails. The
voltages protected are +5VDC, PMC +5VDC, +3.3VDC, +12VDC and
-12VDC. Polyswitches are provided for both USB output voltages and
keyboard/mouse Vcc.
lists the fuses with the voltages they
protect.
Note
*The main supply voltages are protected by an electronic circuit
breaker. The MCP750HA uses an LTC1643 hot swap controller
device from Linear Technologies to implement fold-back current
limiting and overcurrent protection.
Speaker Control
The MCP750HA base board supplies a
SPEAKER_OUT
signal to the
transition module. The transition module contains a two pin jumper header
(J13) which allows the
SPEAKER_OUT
signal to be cabled to an external
speaker to obtain a beep tone.
Table 3-6. Fuse Assignments
Fuse#
Type
Voltage/Purpose/J Number
Fuse
Rating
U63*
Electronic
+3.3VDC for onboard voltage, to J12 PMC connector
and to J3/J4 Transition module connectors.
9.8 Amps
U63
Electronic
+5VDC for onboard voltage and to J3/J4/J5 Transition
module connectors
9.8 Amps
R391
Polyswitch
+5VDC to J5 Transition module connector for
keyboard/mouse voltage (J5 - C21)
1.1 Amps
U63
Electronic
+12VDC to J12 PMC (J12-1) connector and J3
Transition module connector (J3-B19)
1 Amp
U63
Electronic
–12VDC to J11 PMC (J11-2) connector and J3
Transition module connector (J3-C19)
1 Amp
R95
Polyswitch
+5VDC to J18 USB Channel 0 connector (J5-C19)
1.1 Amps
R2
Polyswitch
+5VDC to J17 USB Channel 1 connector (J5-E18)
1.1 Amps