8

FN6342.1

December 7, 2006

Application Block Diagram

Detailed Description

The ISL54205A device is a dual single pole/double throw

(SPDT) analog switch device that operates from a single DC

power supply in the range of 2.7V to 3.6V. It was designed to

function as a dual 2 to 1 multiplexer to select between USB

differential data signals and audio L and R stereo signals. It

players, PDAs, cell phones, and other personal media

players.

The part consists of two 3

Ω audio switches and two 5Ω USB

switches. The audio switches can accept signals that swing

below ground. They were designed to pass audio left and

right stereo signals, that are ground referenced, with minimal

distortion. The USB switches were designed to pass high-

speed USB differential data signals with minimal edge and

phase distortion.

The ISL54205A was specifically designed for MP3 players,

cell phones and other personal media player applications

that need to combine the audio headphone jack and the

USB data connector into a single shared connector, thereby

saving space and component cost. A typical application

block diagram of this functionality is shown above.

The ISL54205A incorporates circuitry for the detection of the

audio CODEC drivers and USB transceiver of the MP3

player or cell phone. The ISL54205A contains a logic control

all switches and puts the part into a low power state, drawing

A detailed description of the two types of switches is

provided in the sections below. The USB transmission and

audio playback are intended to be mutually exclusive

operations.

Audio Switches

The two audio switches (L, R) are 3

Ω switches that can pass

signals that swing below ground. Crosstalk between the

audio switches over the audio band is < -110dB.

variation. They can pass ground referenced audio signals

with very low distortion (<0.06% THD+N) when delivering

15.6mW into a 32

Ω headphone speaker load. See Figures 8,

9, 10, and 11 THD+N performance curves.

These switches are uni-directional switches. The audio

drivers should be connected at the L and R side of the switch

(pins 7 and 8) and the speaker loads should be connected at

the COM side of the switch (pins 3 and 4).

The audio switches are active (turned ON) whenever the

Note: Whenever the audio switches are ON the USB

transceivers need to be in the high impedance state or static

high or low state.

USB Switches

The two USB switches (D+, D-) are 5

Ω bidirectional switches

that are designed to pass high-speed USB differential

signals in the range of 0V to 400mV. The switches have low

capacitance and high bandwidth to pass USB high-speed

signals (480Mbps) with minimum edge and phase distortion

to meet USB 2.0 signal quality specifications. See Figure 12

for High-speed Eye Pattern taken with switch in the signal

path.

The maximum signal range for the USB switches is from

by more than -1.5V.

ISL54205A

USB

TRANSCEIVER

HIGH-SPEED

CODEC

COM -

COM +

GND

D-

D+

L

R

CTRL

LOGIC CIRCUITRY

μCONTROLLER

22k

Ω

4M

Ω

4M

Ω

50k

Ω

50k

Ω

ISL54205A