2
AN1407.0
January 23, 2009
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.
Logic Control
The state of the ISL54210 device is determined by the
voltage at the V
BUS
pin and the CTRL pin. These logic pins
have internal 4M
Ω
pull-down resistors and can be left
floating.
Access to the CTRL pin is through the banana jack J12
(CTRL).
Access to the V
BUS
pin is through banana jack J13 (V
BUS
)
when jumper JP3 is in position 2 to 3 and through the USB
J1 (USB TO HOST) connector V
BUS
line when the jumper
JP3 is in position 2 to 1.
If V
BUS
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.
If V
BUS
is floating (no USB host controller connected at the
J1 connector) and CTRL = Low or Floating, the part will be in
the MUTE mode. In MUTE mode all switches are OPEN and
the click and pop circuitry on the L and R side of the switch is
activated.
If V
BUS
is greater than V
DD
by 0.8V (USB computer V
BUS
line connected at the J1 USB connector), the part will be in the
USB mode. In a typical application, the V
BUS
voltage from
computer/host controller will be in the range of 4.4V to 5.25V
and the V
DD
voltage will be in the range of 2.7V to 3.6V.
When the computer is not connected at J1, the internal
pull-down will pull the V
BUS
pin low putting the ISL54210 in
the Audio mode or Mute mode depending on the condition of
the CTRL pin.
When a USB cable from the computer is connected at J1,
the voltage at the V
BUS
pin will be driven high and the part
will automatically go into the USB mode.
When the USB cable is disconnected from the J1 connector,
the voltage at the V
BUS
pin will be pulled low by the
pull-down resistor and return to the Audio mode or Mute
mode depending on the condition of the CTRL pin.
Note: The evaluation board has the option of putting a 4M
Ω
pull-down resistor from the V
BUS
pin to ground by putting a
jumper at JP4. However, it is not required for the ISL54210
part because the V
BUS
and CTRL pins have internal 4M
Ω
pull-down resistors. These resistors pull the logic pins to
ground when J13, J1, or J12 are floated.
Rather than using the V
BUS
voltage from the computer to
control the V
BUS
logic pin of the part through USB connector
J1 (USB TO HOST), you can drive the V
BUS
pin through the
banana jack J13 (V
BUS
). To control the part through the J13
banana jack make the following connections: Install jumper
JP3 at location 2 to 3. This connects the J13 banana jack to
the V
BUS
pin of the part.
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 an RCA
jack connector. You can connect an audio source/generator
at either the BNC connector or the RCA connector.
In a typical application the left and right outputs of a stereo
source, such as an MP3 player, would be connect to the
RCA jacks J3 and J4, respectfully.
Over a signal range of ±1V (0.707V
RMS
), these switches
have an extremely low r
ON
resistance variation. They can
pass ground referenced audio signals with very low
distortion (<0.05% THD+N) when delivering 15.6mW into a
32
Ω
headphone speaker load. A 3V
P-P
signal is acceptable
but performance will degrade.
The audio channels are AC coupled with 100µF capacitors.
These capacitors 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 0
Ω
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.
Audio Outputs
The evaluation board has a standard headphone jack
labeled HEADPHONE JACK (J7). A 32
Ω
stereo headphone
should be plugged into this jack.
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.
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
up-stream USB host controller, which is usually a PC
computer or hub. When this connection is made, the
ISL54210 device will sense the V
BUS
voltage from the host
controller and go into USB mode. The USB switches will be
turned ON.
An “A” type USB receptacle labeled USB TO DEVICE (J2) is
located on the right under-side of the board. The USB device
Application Note 1407
