ISL54225_10 Datasheet, PDF (11/18 Pages) Intersil Corporation – High-Speed USB 2.0 (480Mbps) Multiplexer with Overvoltage Protection (OVP)

ISL54225
LOGIC CONTROL
The state of the ISL54225 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 ISL54225 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 25µA.
With V_DD = 4.3V and logic pins at 2.6V, the part typically
draws only 35µA. Driving the logic pins to the V_DD supply
rail minimizes power consumption.
The SEL pin and OE pin have special circuitry that allows
them to be driven with a voltage higher than the V_DD
supply voltage. These pins can be driven up to 5.25V
with a V_DD supply in the range of 2.7V to 5.25V.
The SEL pin is internally pulled low through 4MΩ resistor
to ground. The OE pin is internally pulled high through a
4MΩ resistor to VDD. These pins can be tri-stated by a
µProcessor or left floating.
Logic Control Voltage Levels
TABLE 2. LOGIC CONTROL VOLTAGE LEVELS
LOGIC = “0” (LOW)
V_DD SUPPLY
RANGE
OE
SEL
LOGIC = “1”
(HIGH)
OE
SEL
2.7V to 3.6V
≤ 0.5V
≤ 0.5V
or
floating
≥1.4V
or
floating
≥1.4V
3.7V to 4.2V
≤ 0.7V
≤ 0.7V
or
floating
≥1.7V
or
floating
≥1.7V
4.3V to 5.25V ≤ 0.8V
≤ 0.8V
or
floating
≥2.0V
or
floating
≥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 1 is active, a link
will be established between the USB 1 transceiver section
of the media player and the computer. The device will be
able to transmit and receive data from the computer.
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.
All Switches OFF Mode
If the SEL pin = Logic “0” and the OE pin = Logic “1”, all of
the switches will turn OFF (high impedance) and the part
will be put in a low power mode. In this mode, the part
draws only 10µA (max) of current across the operating
temperature range. In the low power mode, the persistence
checking of the OVP circuitry is de-activated.
If the SEL pin = Logic “1” and the OE pin = Logic “1”, all
of the switches will turn OFF (high impedance). In this
state the complete OTV circuitry is activated.
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 ISL54225 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.
Whenever the ISL54225 senses a fault condition on the
COM pins, all switches will be turned OFF regardless of
the voltage levels at the SEL and OE pins.
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 (4.4V to
5.25V) or a -1V short to the D+ or D- signal lines when
the device is either powered off or powered on for at
least 24 hours.
The ISL54225 part has special power-off protection and
OVP detection circuitry to meet these short circuit
requirements. This circuitry allows the ISL54225 to
provide protection to the USB down-stream transceivers
connected at its signal pins (HS1D-, HS1D+, HS2D-,
HS2D+) to meet the USB specification short circuit
requirements.
The power-off protection and OVP circuitry allows the COM
pins (D-, D+) to be driven up to 5.25V or down to -5V while
the V_DD supply voltage is in the range of 0V to 5.25V. In
these overvoltage conditions with a 500Ω external VDD
resistor, the part draws < 55µA of current into the COM pins
and causes no stress/damage to the IC. In addition, all
switches are OFF and the shorted V_BUS voltage will be
isolated from getting through to the other side of the switch
channels, thereby protecting the USB transceivers.
11
FN7627.0
July 2, 2010