10

November 25, 2008

When nothing is plugged into the common connector or a

headphone is plugged into the common connector, the

microprocessor will sense that there is no voltage at the

control pin of the ISL54215 low. As long as CTRL = Logic

“1,” the ISL54215 part will be in the audio mode and the

audio drivers of the media player can drive the headphones

and play music.

USB Mode

If the IN pin = Logic “1” and the CTRL pin = Logic “0” or

Logic “1”, the part will go into USB mode. In USB mode, the

D- and D+ 5

Ω switches are ON and the L and R 2.5Ω audio

switches are OFF (high impedance).

When a USB cable from a computer or USB hub is

connected at the common connector, the µprocessor will

voltage high. The ISL54215 part will go into the USB mode.

In USB mode, the computer or USB hub transceiver and the

MP3 player or cell phone USB transceiver are connected

and digital data will be able to be transmitted back and forth.

When the USB cable is disconnected, the µprocessor will

will drive the IN pin low and put the part back into the Audio

or Low Power Mode.

Low Power Mode

If the IN pin = Logic “0” and CTRL pin = Logic “0”, the part

will be in the Low Power mode. In the Low Power mode, the

audio switches and the USB switches are OFF (high

impedance). In this state, the device draws typically 1nA of

current.

In Low Power mode, the OFF-isolation and crosstalk

between switch cells is minimal for negative swinging

signals. Care should be taken to avoid negative swinging

signals in this mode of operation. In typical applications, the

Low Power state will be applied to the ISL54215 part when

the portable media player is in its sleep or hibernate mode to

conserve battery power. In the sleep mode, no audio or USB

signals are applied to the part.

“IN” PIN

Rather than using a microprocessor to control the IN logic

voltage from the computer or USB hub. See the Application

Block Diagram, Figure 9.

When a headphone or nothing is connected at the common

connector, the internal 4M

Ω pull-down will pull the IN pin low,

putting the ISL54215 in the Audio or Low Power mode,

depending on the condition of the CTRL pin.

When a USB cable is connected at the common connector,

the voltage at the IN pin will be driven to 5V and the part will

automatically go into the USB mode.

When the USB cable is disconnected from the common

connector, the voltage at the IN pin will be pulled low by the

pull-down resistor and return to the Audio or Low Power

mode, depending on the condition of the CTRL pin.

Note: The ISL54215 contains an internal diode between the

IN pin and VDD pin. Whenever the IN voltage is greater than

resistor in the range of 100k

Ω to 500kΩ is required at the IN

voltage is in the range of 2.5V to 3.6V. A 500k

Ω resistor will

limit the current to 2.76µA and still allow the IN logic voltage

level of 1.4V. A smaller series resistor can be used but more

current will flow.

ISL54215