ISL54206A Datasheet, PDF (11/19 Pages) Intersil Corporation – MP3/USB 2.0 High Speed Switch with Negative Signal Handling

ISL54206A
LOGIC CONTROL
The state of the ISL54206A device is determined by the
voltage at the IN pin (pin 2) and the CTRL pin (pin 10).
Refer to “Truth Table” on page 2. 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 µprocessor.
The CTRL pin is internally pulled low through a 4MΩ
resistor to ground and can be left floating or tri-stated by
the µprocessor. The CTRL control pin is only active when
IN is logic “0”.
The IN pin does not have an internal pull-down resistor
and must not be allowed to float. It must be driven High
or Low.
The voltage at the IN pin can exceed the V_DD voltage by
as much as 2.55V. 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 2.7V to 3.6V. An
external pull-down resistor is required from the IN pin to
ground when directly driving the IN pin with the
computer VBUS voltage. See “USING THE COMPUTER
VBUS VOLTAGE TO DRIVE THE “IN” PIN” on page 11.
Logic Control Voltage Levels
IN = Logic “0” (Low) when IN ≤0.5V
IN = Logic “1” (High) when 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) 3Ω audio switches are ON and the D- and D+ 5Ω
USB 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
VBUS pin of the connector and will drive and hold the IN
control pin of the ISL54206A low. As long as the
CTRL = Logic “1,” the ISL54206A 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 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 3Ω
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 VBUS and drive the IN pin
voltage high. The ISL54206A 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 VBUS 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
(high impedance). In this state, the device draws
typically 1nA of current.
USING THE COMPUTER V_BUS VOLTAGE TO DRIVE
THE “IN” PIN
External IN Pull-Down Resistor
Rather than using a microprocessor to control the IN
logic pin you can directly drive the IN pin using the V_BUS
voltage from the computer or USB hub. In order to do
this, you must connect an external resistor from the IN
pin to ground.
When a headphone or nothing is connected at the
common connector, the external pull-down will pull the
IN pin low putting the ISL54206A in the Audio mode 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 Mode or
Low Power Mode depending on the condition of the CTRL
pin.
Note: The voltage at the IN pin can exceed the V_DD
voltage by as much as 2.55V. 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
2.7V to 3.6V.
External IN Series Resistor
The ISL54206A contains a clamp circuit between IN and
VDD. Whenever the IN voltage is greater than the V_DD
voltage by more than 2.55V, current will flow through
this clamp circuitry into the V_DD power supply bus.
During normal USB operation, V_DD is in the range of 2.7V
to 3.6V and IN (V_BUS voltage from computer or USB
hub) is in the range of 4.4V to 5.25V, the clamp circuit is
not active and no current will flow through the clamp into
the V_DD supply.
In a USB application, the situation can exist where the
V_BUS voltage from the computer could be applied at the
IN pin before the V_DD voltage is up to its normal
operating voltage range and current will flow through the
clamp into the V_DD power supply bus. This current could
be quite high when V_DD is OFF or at 0V and could
potentially damage other components connected in the
circuit. In the application circuit, a 22kΩ resistor has
been put in series with the IN pin to limit the current to a
safe level during this situation.
11
FN6515.2
September 30, 2010