isp1520 NXP Semiconductors, isp1520 Datasheet - Page 12

• Manufacturer Part Number: isp1520
• Description: Hi-speed Universal Serial Bus Hub Controller
• Manufacturer: NXP Semiconductors

Philips Semiconductors
ISP1520_4
Product data sheet
Fig 5. Typical voltage drop components in self-powered mode using individual overcurrent detection
(1) Includes PCB traces, ferrite beads, and so on.
POWER SUPPLY
3 % regulated
8.1.2.1 Voltage drop requirements
8.1.2 Power switching
5 V
Table 4.
Power switching of downstream ports can be done individually or ganged, where all
ports are simultaneously switched with one power switch. The ISP1520 supports both
modes, which can be selected using input PSWn_N; see
Self-powered hubs are required to provide a minimum of 4.75 V to its output port
connectors at all legal load conditions. To comply with Underwriters Laboratory Inc. (UL)
safety requirements, the power from any port must be limited to 25 W (5 A at 5 V).
Overcurrent protection may be implemented on a global or individual basis.
Assuming a 5 V
allows a voltage drop of 100 mV across the hub Printed-Circuit Board (PCB) to each
downstream connector. This includes a voltage drop across the:
The PCB resistance and power supply connector resistance may cause a drop of 25 mV,
leaving only 75 mV as the voltage drop allowed across the power switch and overcurrent
sense device. Individual voltage drop components are shown in
For global overcurrent detection, an increased voltage drop is needed for the overcurrent
sense device (in this case, a low-ohmic resistor). This can be realized by using a special
power supply of 5.1 V
Number of physical
downstream facing port
4
3
2
•
•
•
•
+
Power supply connector
Hub PCB (power and ground traces, ferrite beads)
Power switch (FET on-resistance)
Overcurrent sense device
4.85 V (min)
Downstream facing port number pin configuration
power switch
(PSWn_N)
3 % power supply, the worst-case supply voltage is 4.85 V. This only
ISP1520
voltage drop
Rev. 04 — 28 April 2006
3 %, as shown in
75 mV
DM1/DP1
15 k
pull-down
15 k
pull-down
15 k
pull-down
PMOS switch
low-ohmic
resistance
voltage drop
hub board
25 mV
Figure
DM2/DP2
15 k
pull-down
15 k
pull-down
15 k
pull-down
(1)
6.
4.75 V (min)
Table
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
Hi-Speed USB hub controller
DM3/DP3
15 k
pull-down
15 k
pull-down
V
CC
V
D+
D
GND
SHIELD
BUS
004aaa261
5.
Figure
downstream
5.
connector
ISP1520
port
DM4/DP4
15 k
pull-down
V
V
CC
CC
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