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ISL76120 Datasheet, PDF (9/13 Pages) Intersil Corporation – Automotive Grade USB 2.0 High/Full Speed Multiplexer | |||
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ISL76120
The maximum signal range for the HSx switches is from -1V
to VDD. The signal voltage should not be allow to exceed the
VDD voltage rail or go below ground by more than -1V.
The HSx switches are active (turned ON) whenever the IN
voltage is â¥1.4V and the EN logic voltage â¥1.4V when
operated with a 2.7V to 3.6V supply.
ISL76120 Operation
The discussion that follows will discuss using the ISL76120 in
the typical application shown in theâApplication Block
Diagramâ on page 8.
POWER
The power supply connected at the VDD (pin 1) provides the
DC bias voltage required by the ISL76120 part for proper
operation. The ISL76120 can be operated with a VDD
voltage in the range of 2.7V to 5.5V. When used in a USB
application, the VDD voltage should be kept in the range of
3.0V to 5.5V to ensure you get the proper signal levels for
good signal quality.
A 0.01µF or 0.1µF decoupling capacitor should be
connected from the VDD pin to ground to filter out any power
supply noise from entering the part. The capacitor should be
located as close to the VDD pin as possible.
LOGIC CONTROL
The state of the ISL76120 device is determined by the
voltage at the IN pin (pin 2) and the EN pin (pin 10). IN is
only active when the EN pin is logic â1â (High). Refer to the
âTruth Tableâ on page 2.
The EN pin is internally pulled low through a 4MΩ resistor to
ground. For logic â0â (Low) it can be driven low or allowed to
Float. The IN pin must be driven low or high and cannot be
left floating.
Logic control voltage levels:
EN = Logic â0â (Low) when VEN â¤0.5V or Floating.
EN = Logic â1â (High) when VEN â¥1.4V
IN = Logic â0â (Low) when VIN â¤0.5V.
IN = Logic â1â (High) when VIN â¥1.4V
Full-speed Mode
If the IN pin = Logic â0â and the EN pin = Logic â1â, the part
will be in the full-speed mode. In this mode, the FSD1 and
FSD2 switches are ON and the HSD1 and HSD2 switches
are OFF (high impedance). In a typical application, VDD will
be in the range of 2.8V to 3.6V and will be connected to the
battery or LDO of the portable media device. When a
computer or USB hub is plugged into the common USB
connector and the part is in the full-speed mode, a link will
be established between the full-speed driver section of the
media player and the computer. The device will be able to
transmit and receive data from the computer at a data rate of
12Mbps.
High-speed Mode
If the IN pin = Logic â1â and the EN pin = Logic â1â, the part
will go into high-speed mode. In high-speed mode, the
HSD1 and HSD2 switches are ON and the FSD1 and FSD2
switches are OFF (high impedance). When a USB cable
from a computer or USB hub is connected at the common
USB connector and the part is in the high-speed mode, a link
will be established between the high-speed driver section of
the media player and the computer. The device will be able
to transmit and receive data from the computer at a data rate
of 480Mbps.
All Switches OFF Mode
If the IN pin = Logic â0â or Logic â1â and the EN pin = Logic â0â,
all of the switches will turn OFF (high impedance).
The all OFF state can be used to switch between the two
USB sections of the media player. When disconnecting from
one USB device to the other USB device, you can
momentarily put the ISL76120 switch in the âall offâ state in
order to get the computer to disconnect from the one device
so it can properly connect to the other USB device when that
channel is turned ON.
9
FN6711.1
May 29, 2008
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