7

FN6836.0

February 9, 2009

Application Block Diagram

Detailed Description

The ISL54223 device is a dual single pole/double throw

(SPDT) analog switch configured as a DPDT that operates

from a single DC power supply in the range of 1.8V to 3.3V.

It was designed to function as a dual 2-to-1 multiplexer to

select between two USB high-speed differential data signals

in portable battery powered products. It is offered in a small

µTQFN package for use in MP3 players, cameras, PDAs,

cell phones, and other personal media players. The device

has an enable pin to open all switches.

The part consists of four 5.5

Ω high speed (HSx) switches.

These switches have high bandwidth and low capacitance to

pass USB high-speed (480Mbps) differential data signals

with minimal edge and phase distortion. They can also swing

data signals with minimal distortion.

The ISL54223 was designed for MP3 players, cameras, cell

phones, and other personal media player applications that

have multiple high-speed and/or full-speed transceivers

sections and need to multiplex between these USB sources

to a single USB host (computer). A typical application block

diagram of this functionality is previously shown.

A detailed description of the HS switches is provided in the

following section.

High-Speed (HSx) Switches

The HSx switches (HSD1-, HSD1+, HSD2-, HSD2+) are

bi-directional switches that can pass rail-to-rail signals.

When powered with a 1.8V supply, these switches have a

HSD1 and HSD2 switches over this signal range is only

0.072

Ω, ensuring minimal impact by the switches to USB

high speed signal transitions. As the signal level increases,

the switch resistance is nominally 12

Ω. See Figures 7, 8, 9,

10, 11 and 12 in the “Typical Performance Curves” beginning

on page 9.

The HSx switches were specifically designed to pass USB

2.0 high-speed (480Mbps) differential signals in the range of

0V to 400mV. They have low capacitance (6.5pF) and high

bandwidth to pass the USB high-speed signals with

minimum edge and phase distortion to meet USB 2.0 high

speed signal quality specifications. See Figure 13 in the

“Typical Performance Curves” on page 9 for USB

High-speed Eye Pattern taken with switches in the

differential signal paths.

The HSx switches can also pass USB full-speed signals

(12Mbps) with minimal distortion and meet all the USB

requirements for USB 2.0 full-speed signaling. See Figures

14 and 15 in the “Typical Performance Curves” on page 11

for USB Full-speed Eye Patterns taken with switches in the

differential signal paths.

The maximum normal operating signal range for the HSx

more than -0.3V for normal operation.

shorted to one or both of the D-/D+ pins, the ISL54223 has

special fault protection circuitry to prevent damage to the

ISL54223 part. The fault circuitry allows the signal pins

(D-, D+, HSD1-, HSD1+, HSD2-, HSD2+) to be driven up to

0V (ground) all switches are OFF and the fault voltage is

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

PORTABLE MEDIA DEVICE

ISL54223

USB

TRANSCEIVER

HIGH-SPEED

D-

D+

SEL

GND

HSD1-

HSD1+

HSD2-

HSD2+

VDD

OE

LOGIC CIRCUITRY

µCONTROLLER

USB

TRANSCEIVER

FULL-SPEED

VBUS

D-

D+

GND

OR

FULL-SPEED

HIGH_SPEED

OR

#1

#2

ISL54223