an1280

ISL54205AEVAL1Z Evaluation Board User’s
Manual
®
Application Note
December 21, 2006
AN1280.0
Description
The ISL54205AEVAL1Z evaluation board is designed to
provide a quick and easy method for evaluating the
ISL54205A USB/Audio Switch IC.
The ISL54205A device is a unique IC. To use this evaluation
board properly requires a thorough knowledge of the
operation of the IC. Refer to the data sheet for an
understanding of the functions and features of the device.
Studying the device’s truth table along with its pinout
diagram on page 2 of the data sheet is the best way to get a
quick understanding of how the part works.
A picture of the main evaluation board is shown in Figure 1.
The ISL54205A μTQFN IC is soldered onto the evaluation
board. It is located in the center of the board and is
designated as U1.
The ISL54205A IC has two modes of operation called Audio
mode and USB mode. The evaluation board contains
standard Audio and USB connectors to allow the user to
easily interface with the IC to evaluate its functions, features,
and performance in the two modes of operation. For
example, when the board is properly powered, a headphone
can be plugged into the headphone jack (J7) and a stereo
source, such as an MP3 player, can be connected at the
RCA connectors J3 (AUDIO LEFT) and J4 (AUDIO RIGHT)
to play music through the audio switches of the IC. See
Figure 2. You can then turn-off the audio source, remove the
headphones, and attach a USB cable from a computer to the
USB connector J1 (USB TO HOST). This will establish a
connection from the computer through the USB switches of
the IC to the USB device connected at the USB connector J2
(USB TO DEVICE), to send and receive data.
This application note will guide the user through the process
of configuring and using the evaluation board to evaluate the
ISL54205A device in both the Audio mode and the USB
mode.
Features
• Standard USB Connectors
• RCA Audio Input Jacks and Headphone Speaker Jack
• Convenient Test Points and Connections for Test
Equipment
FIGURE 1. ISL54205AEVAL1Z EVALUATION BOARD
(TOP VIEW)
Board Architecture/Layout
Basic Layout of Evaluation Board
The basic layout of the main board is as follows: Refer to
Figure 1.
Power and Ground connections are at the top of the board
(J10 and J11).
Audio Source Inputs are at the lower right side of the board
(J3, J4, J5 and J6). Audio outputs are at the lower left side of
the board (J7, J8, J9). Connector J7 is a standard
headphone jack for connecting a 32Ω headphone.
USB connection to an upstream host controller (Computer)
is made at connector J1, located on left under-side of the
board. USB connection to a downstream USB device is
made at connector J2, located on right under-side of the
board.
Located in the center of the board is the ISL54205A IC (U1).
The eval board has a pin 1 dot, to show how the IC should
be oriented on to the evaluation board. The IC pin 1 indicator
dot needs to be aligned with the evaluation board pin 1 dot
indicator.
Power Supply
The DC power supply connected at banana jacks J10 (VDD)
and J11 (GND) provides power to the part. The IC requires a
2.7V to 3.6V DC power supply for proper operation. The power
supply should be capable of delivering 100μA of current.
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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Application Note 1280
Logic Control
The state of the ISL54205A device is determined by the
voltage at the VBUS pin and the CTRL pin. Access to the
CTRL pin is through the banana jack J12 (CTRL) and
access to the VBUS pin is through the USB J1 connector or
the banana jack J13 (VBUS).
Note: When in USB mode the audio source needs to be in a
high impedance state so it will not interfere with the USB
signal. Since the audio source inputs are AC coupled on the
evaluation board, simply turning the audio source OFF will
isolate it from interfering with the USB signal.
Audio Outputs
If VBUS is floating (no USB host controller connected at the
J1 connector) and CTRL = High (J12 connected to J10), the
part will be in the Audio mode.
The evaluation board has a standard headphone jack
labeled HEADPHONE JACK (J7). A 32Ω stereo headphone
should be plugged into this jack.
If VBUS is floating (no USB host controller connected at the
J1 connector) and CTRL = Low or Floating, the part will be in
the Low Power mode. In Low Power mode all switches are
OPEN and the part will draw around 1nA of current.
The BNC connector J8 (COM-) is in parallel with the audio
left line of the headphone jack and the D- line of the J1 (USB
To HOST) connector. The BNC connector J9 (COM+) is in
parallel with the audio right line of the headphone jack and
the D+ line of the J1 (USB To DEVICE) connector. These
BNC connectors can be used to connect resistive loads
and/or test equipment to evaluate the performance of the IC.
If VBUS is greater than VDD by 0.8V (USB computer VBUS
line connected at the J1 USB connector), the part will be in
the USB mode. In a typical application, the VBUS voltage
from computer/host controller will be in the range of 4.4V to
5.25V and the VDD voltage will be in the range of 2.7V to
3.6V.
Audio Inputs
The evaluation board has two audio inputs labeled AUDIO
LEFT (J3 or J5) and AUDIO RIGHT (J4 or J6). Each of these
inputs have a BNC connector wired in parallel with a RCA
jack connector. You can connect an audio source/generator
at either the BNC connector or the RCA connector.
USB Connections
A “B” type USB receptacle labeled USB TO HOST (J1) is
located on the left under-side of the board. This receptacle
should be connected using a standard USB cable to the upstream USB host controller, which is usually a PC computer
or hub. When this connection is made, the ISL54205A
device will sense the VBUS voltage from the host controller
and go into USB mode. The USB switches will be turned
ON.
In a typical application, the left and right outputs of a stereo
source (such as an MP3 player) would be connected to the
RCA jacks J3 and J4, respectively.
An “A” type USB receptacle labeled USB TO DEVICE (J2) is
located on the right under-side of the board. The USB device
can be plugged directly into this receptacle or through a
standard USB cable.
Over a signal range of ±1V (0.707VRMS) these switches
have an extremely low rON resistance variation. They can
pass ground referenced audio signals with very low
distortion (<0.05% THD+N) when delivering 15.6mW into a
32Ω headphone speaker load. A 3VP-P signal is acceptable
but performance will degrade.
In USB mode the USB host controller and USB device will
be connected through the internal USB switches of the IC.
Unlike the audio switches, the USB switches are
bi-directional, which allow the host (computer) and
downstream USB device to both send and receive data.
The audio channels are AC coupled with 100μF capacitors.
These caps remove any DC voltage from the audio signals
and reference them to ground of the device. If the audio
source being connected to the evaluation board already has
internal AC coupling capacitors at the output of its drivers
then the capacitors on the evaluation board should be
shorted out (replaced with 0Ω resistors). This will prevent
further attenuation of the low frequency content of the audio
signal due to the increase of the high-pass corner frequency
resulting from the evaluation board capacitor in series with
the audio source capacitor.
The audio switches are not bi-directional. The audio source
needs to be connected at J3 or J5 and J4 or J6. Do not try to
apply an audio source at the J8 and J9 BNC connectors on
the left side of the board and at loads J3 through J6 on the
right side of the board.
2
Note: Before connecting the USB host controller at connector
J1, the headphones must be removed from the headphone
speaker jack, J7. This will prevent the audio load from
interfering with USB signal transmission. The main purpose of
the ISL54205A device is to allow the use of a common USB
and Audio Headphone Connector in Personal Media Players
and other portable battery powered equipment. Either a
headphone will be in the common connector to play music or a
USB cable from a computer will be in the common connector to
transmit digital data, such as music, into the memory of the
Media Player.
The BNC connector J8 (COM-) is in parallel with the D- line of
the J1 USB connector. The BNC connector J9 (COM+) is in
parallel with the D+ line of the J1 USB connector. The BNC
connector J13 (VBUS) is in parallel with the VBUS line of the J1
USB connector.
AN1280.0
December 21, 2006
Application Note 1280
Using The Board (Refer to Figure 2)
The BNC connector J14 (D-) is in parallel with the D- line of the
J2 USB connector. The BNC connector J15 (D+) is in parallel
with the D+ line of the J2 USB connector. If you want to use the
J14 and J15 BNC connectors, you must populate R1 and R2
with 0Ω resistors. These BNC connectors can be used to
connect test equipment to evaluate the performance of the IC.
Lab Equipment
The equipment, external supplies and signal sources
needed to operate the board are listed below:
1. +2.7V to 3.6V DC Power Supply
Board Component Definitions
DESIGNATOR
2. Stereo Audio Source (MP3/Radio/CD Player) or Audio
Generator
DESCRIPTION
3. Headphone Set or Audio Analyzer/Oscilloscope
U1
ISL54205AIRUZ IC
4. Two standard USB cables
J1
“B” type USB Receptacle
5. Computer with USB port
J2
“A” type USB Receptacle
6. USB device (i.e. USB memory stick, MP3 Player with
USB port, etc.)
J3, J5
Left Stereo Audio Input
J4, J6
Right Stereo Audio Input
Initial Board Setup Procedure
1. Attach the main evaluation board to a DC power supply
at J10 (VDD) and J11 (GND); positive terminal at J10 and
negative terminal at J11. The supply should be capable of
delivering 2.7V to 3.6V and 100μA of current. Set the
supply voltage to 3.3V.
J7
Headphone Speaker Jack
J8
COM- BNC Connector
J9
COM+ BNC Connector
J10
VDD Positve Connection
J11
VDD Negative Connection
J12
CTRL Logic Control
J13
VBUS Logic Control
(In parallel with J1 USB VBUS line. Control will
typically be through J1 connector)
J14
D- BNC Connector
J15
D+ BNC Connector
JP1, JP2
2. Connect the stereo audio source left channel to J3 RCA
connector or J5 BNC connector, and the right channel to
J4 RCA connector or J6 BNC connector.
3. Connect the USB device to the USB “B” type receptacle,
J2 (USB TO DEVICE).
Audio Mode Operation
1. Install headphone in the headphone jack, J7. No USB
cable should be connected at the J1 (USB TO HOST)
connector.
2. Connect J12 (CTRL) to J10 (VDD). You will now be in
Audio mode (3Ω audio switches are ON).
D-/D+ Differential Probe Connection
3. Turn the audio source ON. You should hear the music in
the headphones.
DC POWER
SUPPLY
+3.3V
+
-
COMPUTER
USB DEVICE
USB PORT
USB PORT
VBUS
J13
VDD
CTRL
GND
J11
J10
J12
J14
USB TO HOST
USB
TO
DEVICE
U1
J1
J2
JP2
JP1
J15
J7
HEADPHONE
JACK
J8
AUDIO LEFT
J5
J3
J6
J4
AUDIO
SOURCE
L
J9
COM - COM +
AUDIO RIGHT
ISL54205A EVALUATION BOARD
R
FIGURE 2. BASIC EVALUATION TEST SETUP BLOCK DIAGRAM
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December 21, 2006
Application Note 1280
4. You can observe the audio signals at the output of the IC
on an oscilloscope or audio analyzer by using the J8 and
J9 BNC connectors. Connect to J8 for left audio and J9
for right audio.
USB Mode Operation
Test Points
The board has various test points for ease of connecting
probes to make measurements. The test points available are
described in the following table.
1. Turn OFF audio stereo source.
2. Remove headphone from J7 Headphone Jack.
3. Connect USB cable from host (PC computer) to the USB
“A” type receptacle, J1 (USB TO HOST). You will now be
in USB mode (5.5Ω USB switches are ON).
4. You should now be able to send and receive data
between the host and USB device.
5. You can observe the D- and D+ USB digital signals on an
oscilloscope or other test equipment by connecting to the
J8, J14, J9 and J15 BNC connectors. Connect to J8/J14
for D- signal and to J9/J15 for D+ signal. The VBUS
voltage from the host can be monitored by connecting a
voltmeter at the J13 BNC connector.
6. Remove the 0Ω resistors R1, R2, R3, R4 when
evaluating the performance (i.e. eye diagram, etc.) of the
high speed USB signal. Removal of these resistors
disconnects the headphone jack (J7) and BNC
connectors (J8, J9, J14, J15) from the USB differential
lines. These components when connected will degrade
the USB signal. These components will not be there in an
actual application. Note: R3 and R4 are located on the
underside of the board.
DESIGNATOR
TP1
DESCRIPTION
VDD test point
TP2, TP6, TP7, Ground Test Point
TP8, TP9
TP3
VBUS Test Point
TP4
Audio Left Input Test Point
TP5
Audio Right Input Test Point
JP1
D-/D+ Differential Probe Connection - USB Device
Side of Switch
JP2
D-/D+ Differential Probe Connection - COM Side of
Switch
If you disconnect the USB cable from J1, the IC will return to
Audio mode. You can now plug the headphone set into the
headphone jack. Turn the audio source ON to once again
play music.
4
AN1280.0
December 21, 2006
Application Note 1280
Board Schematic
1
DJ14
2 34 5
A
GND
VDD
1
J10
J11
C1
1
VDD
1
10UF
C2
C5
VBUS
3
4
0
0
R4
R3
2
TP6
PACKAGE
46
9
8
8
7
7
2
3
+
4
6
JP1
1
TP8
TP7
6
HEADPHONE
JACK
J7
J8
COM-
J9
COM+
5 4 3
TO
DEVICE
MOUNT
J2
TP9
1
1
A
C3
R
TP5
J3
2
100UF
3 4
1
AUDIO LEFT
J5
2 34 5
1
1
5 4 3
2
USB
1
L
A
1
4
3
5
2
6
1
TP4
1
J1
DNP
R1
9
MOUNT
1
JP2
1
3
U1
QFN
10 PIN
1
5
1
4
1
1
2
5
D-
5
USB
COM1
COM2
MOUNT
A
1
2
2
DNP
R2
10
0
10
R5
DNP
2
3
4
897-30-004-90-000
TO
HOST
CTRL
DUSB_ARA42_T11A
1 24 3
5
3
J12
1
0
R6
MOUNT
USB
A
1
R7
1
J13
J15
2 34 5
TP3
1
0.1UF
OPEN
1
TP1
TP2
D+
2
1
C4
2
100UF
J4
3 4
1
2
1
AUDIO RIGHT
J6
34 5
2
A
Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to
verify that the Application Note or Technical Brief is current before proceeding.
For information regarding Intersil Corporation and its products, see www.intersil.com
5
AN1280.0
December 21, 2006
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