ISL54209 Datasheet, PDF (12/19 Pages) Intersil Corporation – MP3/USB 2.0 High Speed Switch with Negative Signal Handling and Low Power Shutdown

ISL54209
part can operate with a supply voltage in the range of
2.5V to 5.0V.
In a typical USB/Audio application for portable battery
powered devices, the V_DD voltage will come from a
battery or an LDO and be in the range of 2.7V to 3.6V.
For best possible USB full-speed operation (12Mbps), it is
recommended that the V_DD voltage be ≥ 2.5V in order to
get a USB data signal level above 2.5V.
LOGIC CONTROL
The state of the ISL54209 device is determined by the
voltage at the IN pin and the CTRL pin. These logic pins
are 1.8V logic compatible when V_DD is in the range of
2.7V to 3.6V and can be controlled by a standard
microprocessor. The part has three states or modes of
operation. The Audio Mode, USB Mode and the Low
Power Mode. Refer to the “Truth Table” on page 2.
The IN and CTRL pins are internally pulled low through a
4MΩ resistor to ground and can be left floating or
tri-stated by the microprocessor. The CTRL control pin is
only active when IN is logic “0”.
Logic control voltage levels:
IN = Logic “0” (Low) when V_IN ≤ 0.5V or Floating.
IN = Logic “1” (High) when V_IN ≥ 1.4V
CTRL = Logic “0” (Low) when ≤ 0.5V or Floating.
CTRL = Logic “1” (High) when ≥ 1.4V
Audio Mode
If the IN pin = Logic “0” and CTRL pin = Logic “1”, the
part will be in the Audio mode. In Audio mode, the L
(left) and R (right) 2.5Ω audio switches are ON and the
D- and D+ 5Ω switches are OFF (high impedance).
When nothing is plugged into the common connector or a
headphone is plugged into the common connector, the
µprocessor will sense that there is no voltage at the V_BUS
pin of the connector and will drive and hold the IN control
pin of the ISL54209 low. As long as CTRL = Logic “1,” the
ISL54209 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+ 5Ω 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
sense the presence of the 5V V_BUS and drive the IN pin
voltage high. The ISL54209 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
sense that the 5V V_BUS voltage is no longer connected
and 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.
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 ISL54209 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.
USING THE COMPUTER V_BUS VOLTAGE TO DRIVE
THE “IN” PIN
Rather than using a microprocessor to control the IN
logic pin, one can directly drive the IN pin using the 5V
V_BUS voltage from the computer or USB hub. See
Figure 9 “Typical Application Block Diagrams” on
page 10.
When a headphone or nothing is connected at the
common connector, the internal 4MΩ pull-down will pull
the IN pin low, putting the ISL54209 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 ISL54209 contains an internal diode between
the IN pin and VDD pin. Whenever the IN voltage is
greater than the V_DD voltage by more than 0.7V, current
will flow through this diode into the V_DD power supply
bus. An external series resistor in the range of 100kΩ to
500kΩ is required at the IN logic pin to limit the current
when driving it with the V_BUS voltage. This allows the
V_BUS voltage from a computer or USB hub (4.4V to
5.25V) to drive the IN pin while the V_DD voltage is in the
range of 2.5V to 3.6V. A 500kΩ resistor will limit the
current to 2.76µA and still allow the IN logic voltage to go
to around 3.67V, which is will above the required V_INH
level of 1.4V. A smaller series resistor can be used but
more current will flow.
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FN6627.4
June 10, 2010