VULCAN Technical Manual
Power and power management
© 2007 Eurotech Ltd Issue D
40
USB power management
A USB power control switch controls the power and protects against short-circuit and
overcurrent conditions.
If the USB voltage VBUSx is short-circuited, or more than 500mA is drawn from any
VBUSx supply, the switch turns off the power supply and protects the device and board
automatically. The VBUSx power supplies are derived from the 5V supply.
The ISP1561 USB host controller provides an advanced power management
capabilities interface that is compliant with PCI bus Power Management Interface
Specification, Rev. 1.1. Power is controlled and managed by the interaction between
drivers and PCI registers. Please refer to the ISP1561 datasheet on the Development
Kit CD for more information about power management.
The ISP1561 USB Host Controller supports four USB ports. Two of the ports can be
disabled if not used by setting the SEL2PORTS pin high. MFUNC4 pin on the PCI1520
device should be configured as GP output and can be used to control the SEL2PORTS
pin of the ISP1561 controller. Disabling two of the ports can reduce the power
consumption of the VULCAN by up to 165mW.
MFUNC4 (SEL2PORTS)
ISP1561 Operation Status
0
All ports enabled
1
Ports 3,4 disabled
Clock generator power management
Two clock generator ICs can be placed in low power mode by shutting down the clock
outputs in case the corresponding interfaces are not used. The following clocks are
affected:
•
XR16L2551 DUART 1.8432MHZ clock.
•
Ethernet PHY 25MHz clock.
•
PC/104 8MHz and 14MHz clocks.
MFUNC1 pin on the PCI1520 device should be configured as GP output and can be
used to control the SHUTDOWN# pin of clock generator IC’s. This can reduce the
power consumption of the VULCAN by up to 130mW.
MFUNC1 (CLK_SHDOWN#)
Clock Operation Status
0 Shutdown
mode
1 Normal
operation
