ISL54221 Datasheet, PDF (8/13 Pages) Intersil Corporation – High-Speed USB 2.0 (480Mbps) Multiplexer

ISL54221
all switches are OFF and the fault voltage is isolated from
the other side of the switch. When V_DD is in the range of
2.7V to 5.5V the fault voltage will pass through to the output
of an active switch channel.
The HS1 channel switches are active (turned ON) whenever
the SEL voltage is logic”0”(Low) and the OE voltage is
logic”0”(Low).
The HS2 channel switches are active (turned ON) whenever
the SEL voltage is logic “1” (High) and the OE voltage is
logic “0” (Low).
ISL54221 Operation
The following will discuss using the ISL54221 the “Application
Block Diagram” on page 7.
POWER
The power supply connected at the VDD pin provides the
DC bias voltage required by the ISL54221 part for proper
operation. The ISL54221 can be operated with a V_DD
voltage in the range of 2.7V to 5.5V. When used in a USB
application, the V_DD 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.
In a typical application, V_DD will be in the range of 2.8V to
4.3V and will be connected to the battery or LDO of the
portable media device.
LOGIC CONTROL
The state of the ISL54221 device is determined by the
voltage at the SEL pin and the OE pin. SEL is only active
when the OE pin is logic “0” (Low). Refer to “Truth Table” on
page 2.
The ISL54221 logic pins are designed to minimize current
consumption when the logic control voltage is lower than the
V_DD supply voltage. With V_DD = 3.6V and logic pins at 1.4V
the part typically draws only 6.6µA. With V_DD = 4.3V and
logic pins at 2.6V the part typically draws only 0.2µA. Driving
the logic pins to the V_DD supply rail minimizes power
consumption.
The logic pins must be held High or Low and must not float.
Logic Control Voltage Levels
With V_DD supply voltage in the range of 2.7V to 3.6V the
logic levels are:
OE = Logic “0” (Low) when V_OE ≤ 0.5V
OE = Logic “1” (High) when V_OE ≥ 1.4V
SEL = Logic “0” (Low) when V_SEL ≤ 0.5V
SEL = Logic “1” (High) when V_SEL ≥ 1.4V
With V_DD supply voltage in the range of 4.3V to 5.5V the
logic levels are:
OE = Logic “0” (Low) when V_OE ≤ 0.8V
OE = Logic “1” (High) when V_OE ≥ 2.0V
SEL = Logic “0” (Low) when V_SEL ≤ 0.8V
SEL = Logic “1” (High) when V_SEL ≥ 2.0V
HSD1 USB Channel
If the SEL pin = Logic “0” and the OE pin = Logic “0”,
high-speed Channel 1 will be ON. The HSD1- and HSD1+
switches are ON and the HSD2- and HSD2+ switches are
OFF (high impedance).
When a computer or USB hub is plugged into the common
USB connector and channel one is active, a link will be
established between the USB 1 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.
HSD2 USB Channel
If the SEL pin = Logic “1” and the OE pin = Logic “0”,
high-speed Channel 2 will be ON. The HSD2- and HSD2+
switches are ON and the HSD1- and HSD1+ 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 has
Channel 2 active, a link will be established between the USB
2 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 SEL pin = Logic “0” or Logic “1” and the OE pin =
Logic “1”, 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 ISL54221 switch in the “all off” 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.
USB 2.0 V_BUS Short Requirements
The USB specification in section 7.1.1 states a USB device
must be able to withstand a V_BUS short to the D+ or D-
signal lines when the device is either powered off or
powered on for at least 24 hours. The ISL54220 part has
special fault protection circuitry to meet these short circuit
requirements.
The fault protection circuitry allows the signal pins (D-, D+,
HS1D-, HS1D+, HS2D-, HS2D+) to be driven up to 5.5V
while the V_DD supply voltage is in the range of 0V to 5.5V. In
this overvoltage condition the part draws < 500µA of current
and causes no stress/damage to the IC.
8
FN6820.0
December 16, 2008