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Philips Semiconductors
6. Functional description
6.1 Analog transceivers
9397 750 07002
Product specification
Table 3:
Pin description for LQFP32
[1]
Symbol
Pin
Type
DM2
26
AI/O
DP2
27
AI/O
[3]
PSW1/GL1
28
O
[1]
Symbol names with an overscore (e.g. NAME) indicate active LOW signals.
[2]
The voltage at pin V
reg(3.3)
connecting RESET to V
BUS
[3]
See
Table 4 "Mode
selection".
[4]
To disable a downstream port connect both D and D to V
be disabled in reverse order starting from port 5.
[5]
Analog detection circuit can be switched off using an external EEPROM, see
the pin functions as a logic input (TTL level).
[6]
Downstream ports 1 and 2 cannot be disabled.
The ISP1122 is a stand-alone USB hub with up to 5 downstream ports. The number
of ports can be configured between 2 and 5. The downstream ports can be used to
connect low-speed or full-speed USB peripherals. All standard USB requests from
the host are handled by the hardware without the need for firmware intervention. The
block diagram is shown in
The ISP1122 requires only a single supply voltage. An internal 3.3 V regulator
provides the supply voltage for the analog USB data transceivers.
The ISP1122 supports both bus-powered and self-powered hub operation. When
using bus-powered operation a downstream port cannot supply more than 100 mA to
a peripheral. In case of self-powered operation an external supply is used to power
the downstream ports, allowing a current consumption of max. 500 mA per port.
2
A basic I
C-bus interface is provided for reading vendor ID, product ID and
configuration bits from an external EEPROM upon a reset.
The integrated transceiver interfaces directly to the USB cables through external
termination resistors. They are capable of transmitting and receiving serial data at
both 'full-speed' (12 Mbit/s) and 'low-speed' (1.5 Mbit/s) data rates. The slew rates
are adjusted according to the speed of the device connected and lie within the range
mentioned in the USB Specification Rev. 1.1 .
Rev. 03 — 29 March 2000
...continued
Description
downstream port 2 D connection (analog)
downstream port 2 D connection (analog)
modes 4 to 6: power switch control output for downstream
port 1 (open-drain, 6 mA)
modes 0 to 3, 7: GoodLink LED indicator output for
downstream port 1 (open-drain, 6 mA); to connect an LED
use a 330
series resistor
is gated by the RESET pin. This allows fully self-powered operation by
(+5 V USB supply). If V
is lost upstream port D+ will not be driven.
BUS
Figure
1.
ISP1122
USB stand-alone hub
[6]
[6]
via a 1 M resistor; unused ports must
CC
Table
23; in this case,
© Philips Electronics N.V. 2000. All rights reserved.
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