ISL54400 Datasheet, PDF (11/15 Pages) Intersil Corporation – Low Voltage, Dual SPDT, USB/Audio Switches with Negative Signal Capability

ISL54400, ISL54401, ISL54402
where the two SPDT switches work in tandem, the ISL54402
gives you independent control over each SPDT switch.
USB Switches
The two NO (normally open) USB switches (D+, D-, NOx)
are 5Ω bidirectional switches that are designed to pass low
speed and full-speed USB differential signals typically in the
range of 0V to 3.6V. The switches have low capacitance and
high bandwidth to pass USB full-speed signals (12Mbps)
with minimum edge and phase distortion to meet USB 2.0
signal quality specifications. See eye diagram Figure 11 on
page 13.
For the ISL54400 and ISL54401 parts, the maximum signal
range for the USB switches is from -1.5V to V_BUS. The
signal voltage should not be allowed to exceed the V_BUS
voltage rail or go below ground by more than -1.5V.
For the ISL54402 part, the maximum signal range is from
-1.5V to V_DD. The signal voltage should not be allowed to
exceed the V_DD voltage rail or go below ground by more
than -1.5V.
When using the ISL54400 and ISL54401 parts, the USB
switches are active (turned ON) whenever the V_BUS voltage
is ≥ to V_DD + 0.8V. V_BUS is internally pulled low, so when
V_BUS is floating the USB switches are OFF.
Note: Whenever the USB switches are ON the audio drivers
of the CODEC, connected at R and L (pins 6 and 7), need to
be at AC or DC ground or floating to keep from interfering
with the data transmission.
When using the ISL54402 part, the NO1 USB switch is
active (turned ON) whenever logic pin IN1 (pin 10) is HIGH.
The NO2 USB switch is active (turned ON) whenever the
logic pin IN2 (pin 2) is HIGH. Unlike the ISL54400 and
ISL54401 parts where the two SPDT switches work in
tandem, the ISL54402 gives you independent control over
each SPDT switch.
ISL54400 and ISL54401 Operation
The ISL54400 and ISL54401 function the same except the
ISL54401 does not have the V_TERM feature. The discussion
that follows pertains to both devices and will discuss using the
parts in the typical application shown in the block diagram on
page 10.
LOGIC CONTROL
The state of the ISL54400 and ISL54401 devices are
determined by the voltage at the V_BUS pin (pin 2). The V_BUS
pin is internally pulled low and can be left floating.
If V_BUS (pin 2) is floating or the V_BUS voltage ≤ V_DD + 0.2V
the part will be in the Audio mode. In Audio mode the L (left)
and R (right) 1Ω audio switches are ON and the D- and D+
5Ω switches are OFF (high impedance). In this state, power
to the part will be provided by the DC voltage connected at
the V_DD pin (pin 1). In a typical application V_DD will be in the
range of 2.5V to 3.6V and will be connected to the battery or
LDO of the MP3 player or cellphone. When a headphone is
plugged into the common connector, nothing gets connected
at the V_BUS pin (it’s floating) and the ISL54400 and
ISL54401 parts remain in the audio mode and the MP3
player or cellphone audio drivers can drive the headphones
and play music.
If V_BUS (pin 2) voltage is greater than V_DD by 0.8V the part
will go into USB mode. In USB mode the D- and D+ 5Ω
switches are ON and the L and R 1Ω audio switches are
OFF (high impedance). In this state the part will be powered
by the voltage connected at the V_BUS pin (pin 2). When a
USB cable from a computer or USB hub is connected at the
common connector the V_BUS voltage is driven to between
4.4V and 5.25V. The ISL54400 and ISL54401 parts will go
into the USB mode. In USB mode the computer or USB hub
transceiver and the MP3 player or cellphone USB
transceiver are connected and digital data will be able to be
transmitted back and forth.
When the USB cable is disconnected the switch
automatically turns the D+ and D- switches OFF and turns
the L and R audio switches ON.
POWER
In audio mode the power supply connected at V_DD (pin 1)
provides power to the ISL54400 and ISL54401 parts. Its
voltage should be kept in the range of 2.5V to 3.6V when
used in a USB/Audio application to ensure you get proper
switching when the V_BUS voltage is at its lower limit of 4.4V.
In USB mode power for the ISL54400 and ISL54401 parts is
provided from the V_BUS line from the host USB controller of
the computer or USB hub. Its voltage will be between 4.4V
and 5.25V.
V_TERM OPERATION (ISL54400 ONLY)
When a USB cable from a computer is connected to a USB
device a V_TERM voltage must be applied to a speed
indicating pull-up resistor to properly terminate the bus and
identify whether the USB device is a full-speed or low-speed
device to facilitate proper digital transmission. When the
cable is removed from the device this V_TERM voltage must
be disconnected from the speed indicating pull-up resistor.
The ISL54400 device can perform this operation.
When V_DD ≥ 2.5V and V_BUS ≥ V_DD + 0.8V, the V_TERM pin
(pin 10) outputs an open circuit voltage equal to the voltage
at the V_BUS pin. Otherwise the V_TERM pin will be in a HI-Z
state.
The ISL54400 V_TERM circuitry has an internal series resistor
approximately equal to 5.3kΩ. For a full speed USB
application, it is recommended you use a 3kΩ ±5% speed
indicating pull-up resistor. When the USB bus is in the idle
state, a 3kΩ ±5% resistor will put the D+ line voltage in the
range of 2.7V to 3.6V as required by the USB specification.
For low-speed USB application, it is recommended you use
11
FN6240.3
July 12, 2006