ISP1130DL Philips Semiconductors, ISP1130DL Datasheet - Page 52

• Manufacturer Part Number: ISP1130DL
• Description: Universal Serial Bus compound hub with integrated keyboard controller
• Manufacturer: Philips Semiconductors

12. Hub power modes
Philips Semiconductors
9397 750 06895
Objective specification
Fig 9. Typical voltage drop components in bus-powered mode (no overcurrent detection).
handbook, full pagewidth
(1) Includes PCB traces, ferrite beads, etc.
connector
upstream
port
12.1.1 Bus-powered hubs
12.1 Voltage drop requirements
SHIELD
V BUS
GND
D
D
USB hubs can either be self-powered or bus-powered.
Self-powered — Self-powered hubs have a 5 V local power supply on board which
provide power to the hub and the downstream ports. The USB Specification Rev. 1.1
requires that these hubs limit the current to 500 mA per downstream port and report
overcurrent conditions to the host. The hub may optionally draw 100 mA from the
USB supply (V
Bus-powered — Bus-powered hubs obtain all power from the host or an upstream
self-powered hub. The maximum current is 100 mA per downstream port. Current
limiting and reporting of overcurrent conditions are both optional.
The ISP1130 has bus-powered downstream ports and supports individual power
switching via pins PSWn.
Bus-powered hubs are guaranteed to receive a supply voltage of 4.5 V at the
upstream port connector and must provide a minimum of 4.4 V to the downstream
port connectors. The voltage drop of 100 mV across bus-powered hubs includes:
The PCB resistance may cause a drop of 25 mV, which leaves 75 mV for the power
switch and overcurrent sense device. The voltage drop components are shown in
Figure
For bus-powered hubs overcurrent protection is optional. It may be implemented for
all downstream ports on a global or individual basis. The ISP1130 has individual
overcurrent protection for its downstream ports.
•
•
•
4.50 V(min)
Hub PCB (power and ground traces, ferrite beads)
Power switch (FET on-resistance)
Overcurrent sense device.
9.
BUS
ISP1122
power
switch
) to power the interface functions (hybrid-powered).
Rev. 01 — 23 March 2000
voltage drop
75 mV
PMOS switch
low-ohmic
USB compound hub with keyboard controller
voltage drop
hub board
resistance
25 mV
(1)
4.40 V(min)
© Philips Electronics N.V. 2000. All rights reserved.
V BUS
D
D
GND
SHIELD
MGR783
ISP1130
downstream
connector
port
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