ISP1521 Просмотр технического описания (PDF) - Philips Electronics
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ISP1521 Datasheet PDF : 53 Pages
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Philips Semiconductors
ISP1521
Hi-Speed USB hub controller
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 ± 3 %, as shown in Figure 6.
The PCB resistance may cause a drop of 25 mV, which leaves 75 mV for the power
switch and overcurrent sense device.
5V
+
POWER SUPPLY
± 3 % regulated −
4.85 V (min)
voltage drop
75 mV
ISP1521
power switch
(PSWn_N)
low-ohmic
PMOS switch
voltage drop
25 mV
4.75 V (min)
hub board
resistance
(1)
VBUS
D+
D−
GND
SHIELD
downstream
port
connector
004aaa264
(1) Includes PCB traces, ferrite beads, and so on.
Fig 5. Typical voltage drop components in the self-powered mode using individual overcurrent detection.
5.1 V KICK-UP +
POWER SUPPLY
± 3 % regulated −
voltage drop
4.95 V(min) 100 mV
low-ohmic
sense resistor
for overcurrent
detection
voltage drop
75 mV
low-ohmic
PMOS switch
ISP1521 power
switch
(PSWn_N)
voltage drop
25 mV 4.75 V(min)
hub board (1)
resistance
VBUS
D+
D−
GND
SHIELD
004aaa265
downstream
port
connector
(1) Includes PCB traces, ferrite beads, and so on.
Fig 6. Typical voltage drop components in the self-powered mode using global overcurrent detection.
PSWn_N pins have integrated weak pull-up resistors inside the chip.
Table 5: Power switching mode: pin configuration
Power switching mode PSW1_N PSW2_N PSW3_N
None
ground
ground
ground
Ganged
internal
pull-up
ground
ground
Individual
internal
pull-up
internal
pull-up
internal
pull-up
PSW4_N
ground
ground
internal
pull-up
PSW5_N
ground
ground
internal
pull-up
PSW6_N
ground
ground
internal
pull-up
PSW7_N
ground
ground
internal
pull-up
9.1.3 Overcurrent protection mode
The ISP1521 supports all overcurrent protection modes: none, global and individual.
No overcurrent protection mode reporting is selected when pin NOOC = HIGH.
Global and individual overcurrent protection modes are selected using pins PSWn_N,
following the power switching modes selection scheme; seeTable 6.
For the global overcurrent protection mode, only PSW1_N and OC1_N are active;
that is, in this mode, the remaining overcurrent indicator pins are disabled. To inhibit
the analog overcurrent detection, the OC_N pins must be connected to VREF(5V0).
9397 750 13702
Product data
Rev. 03 — 24 November 2004
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
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