Philips Semiconductors
ISP1122A
USB stand-alone hub
6.9 PLL clock multiplier
A 6 to 48 MHz clock multiplier Phase-Locked Loop (PLL) is integrated on-chip. This
allows for the use of low-cost 6 MHz crystals. The low crystal frequency also
minimizes Electro-Magnetic Interference (EMI). The PLL requires no external
components.
6.10 Overcurrent detection
An overcurrent detection circuit for downstream ports has been integrated on-chip. It
is self-reporting, resets automatically, has a low trip time and requires no external
components. Both individual and global overcurrent detection are supported.
6.11 I
2
C-bus interface
A basic serial I
2
C-bus interface (single master, 100 kHz) is provided to read VID, PID
and configuration bits from an external I
2
C-bus EEPROM (e.g. Philips PCF8582 or
equivalent). At reset the ISP1122A reads 6 bytes of data from the external memory.
The I
2
C-bus interface timing complies with the standard mode of operation as
described in
The I
2
C-bus and how to use it,
order number 9398 393 40011.
7. Modes of operation
The ISP1122A has several modes of operation, each corresponding with a different
pin configuration. Modes are selected by means of pins INDV, OPTION and SP/BP,
as shown in
Table 4.
Table 4:
Mode
0
1
2
3
4
5
6
7
Mode selection
INDV
[1]
OPTION SP/BP
[2]
PSWn/GLn
(n = 1 to 4)
GoodLink
GoodLink
GoodLink
GoodLink
[4]
individual power
individual power
individual power
GoodLink
[4]
PSW5/GL5/GPSW OCn
(n = 1 to 4)
ganged power
ganged power
ganged power
GoodLink
[4]
inactive
individual power
inactive
GoodLink
[4]
inactive
inactive
inactive
[3]
inactive
individual
overcurrent
individual
overcurrent
inactive
[3]
individual
overcurrent
OC5/GOC
global overcurrent
global overcurrent
inactive
[3]
global overcurrent
inactive
individual
overcurrent
inactive
[3]
individual
overcurrent
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
[1]
[2]
[3]
[4]
Port power switching: logic 0 = ganged, logic 1 = individual.
Power mode: logic 0 = bus-powered, logic 1 = self-powered (or hybrid-powered).
No overcurrent detection.
No power switching.
9397 750 06986
© Philips Electronics N.V. 2000. All rights reserved.
Preliminary specification
Rev. 01 — 27 March 2000
10 of 48
PHILIPS [ NXP SEMICONDUCTORS ]
