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ISP1122A

Universal Serial Bus stand-alone hub

Philips Electronics 

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 I2C-bus interface

A basic serial I2C-bus interface (single master, 100 kHz) is provided to read VID, PID

and configuration bits from an external I2C-bus EEPROM (e.g. Philips PCF8582 or

equivalent). At reset the ISP1122A reads 6 bytes of data from the external memory.

The I2C-bus interface timing complies with the standard mode of operation as

described in The I2C-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 selection

Mode INDV

[1]

OPTION SP/BP

[2]

0

0

0

0

1

0

0

1

2

0

1

0

3

0

1

1

4

1

0

0

PSWn/GLn

(n = 1 to 4)

GoodLink

GoodLink

GoodLink

GoodLink [4]

individual power

5

1

0

1

individual power

6

1

1

0

individual power

7

1

1

1

GoodLink [4]

PSW5/GL5/GPSW OCn

(n = 1 to 4)

ganged power

inactive

ganged power

inactive

ganged power

inactive [3]

GoodLink [4]

inactive

inactive

individual

overcurrent

individual power

individual

overcurrent

inactive

inactive [3]

GoodLink [4]

individual

overcurrent

OC5/GOC

global overcurrent

global overcurrent

inactive [3]

global overcurrent

inactive

individual

overcurrent

inactive [3]

individual

overcurrent

[1] Port power switching: logic 0 = ganged, logic 1 = individual.

[2] Power mode: logic 0 = bus-powered, logic 1 = self-powered (or hybrid-powered).

[3] No overcurrent detection.

[4] No power switching.

9397 750 06986

Preliminary specification

Rev. 01 — 27 March 2000

© Philips Electronics N.V. 2000. All rights reserved.

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