8

FN6835.0

February 9, 2009

range of 1.8V to 3.3V the fault voltage will pass through to

the output of an active switch channel. During the fault

condition normal operation is not guaranteed until the fault is

section below.

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).

ISL54222 Operation

The following will discuss using the ISL54222 shown in the

“Application Block Diagram” on page 7.

POWER

bias voltage required by the ISL54222 part for proper

voltage in the range of 1.8V to 3.3V.

A 0.01µF or 0.1µF decoupling capacitor should be

supply noise from entering the part. The capacitor should be

LOGIC CONTROL

The state of the ISL54222 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 the “Truth Table”

on page 2.

The ISL54222 logic pins are designed to minimize current

consumption when the logic control voltage is lower than the

supply rail minimizes power consumption.

The logic pins must be held High or Low and must not float.

Logic Control Voltage Levels

logic levels are:

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 Channel 2 is

active, a link will be established between the USB 2

transceiver 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” 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 switching from one

USB transceiver section to the other USB transceiver

section, you can momentarily put the ISL54222 switch in the

“ALL OFF” state, in order to get the computer to disconnect

from the current USB section, so it can properly connect to

the other USB transceiver section when that channel is

turned ON.

The USB 2.0 specification in chapter 7, section 7.1.1 states

D+ or D- signal lines when the device is either powered off or

powered on for at least 24 hours. The ISL54222 part has

special fault protection circuitry to meet these short circuit

requirements.

The fault protection circuitry allows the signal pins (D-, D+,

HSD1-, HSD1+, HSD2-, HSD2+) to be driven up to 5.5V

current and causes no stress/damage to the IC.

of the switch.

voltage will pass through to the output of an active (turned

ON) switch channel but not through a turned OFF channel.

Any components connected on the active channel must be

able to withstand the overvoltage condition.

Note: During the fault condition normal operation of the USB

channel is not guaranteed until the fault condition is

removed.

ISL54222