ISL54213 Datasheet, PDF (9/15 Pages) Intersil Corporation – MP3/USB 2.0 High Speed Switch with Negative Signal Handling and Mute Function

ISL54213
data connector into a single shared connector, thereby
saving space and component cost. Typical Application Block
Diagrams of this functionality are shown in Figures 8 and 9.
The ISL54213 has a single logic control pin (IN) that selects
between the audio switches and the USB switches. This pin
can be driven Low or High to switch between the audio
CODEC drivers and USB transceiver of the MP3 player or
cellular phone. The ISL54213 also contains a logic control
pin (CTRL) that when driven Low while IN is Low, opens all
switches and puts the part into the mute state.
A detailed description of the two types of switches are
provided in the following sections.
Audio Switches
The two audio switches (L, R) are 2.5Ω switches that can
pass signals that swing below ground by as much as 1.5V.
They were designed to pass ground reference stereo signals
with minimal insertion loss and very low distortion over a ±1V
signal range.
Crosstalk between the audio channels is -112dB over the
audio band. Crosstalk between the audio channel and USB
channel is -95dB at 100kHz. These switches have excellent
off-isolation, 112dB, over the audio band with a 32Ω load.
Over a signal range of ±1V (0.707V_RMS) with VDD > 2.7V,
these switches have an extremely low r_ON resistance
variation. They can pass ground referenced audio signals with
very low distortion (<0.06% THD+N) when delivering 15.6mW
into a 32Ω headphone speaker load. See Figures 10 and 11.
These switches are bi-directional switches. In typical
applications, the audio drivers would be connected at the
L and R side of the switch (pins 7 and 8) and the speaker
loads would be connected at the COM side of the switch
(pins 3 and 4).
The audio switches are active (turned ON) whenever the IN
voltage is ≤ 0.5V or floating and the CTRL voltage ≥ to 1.4V.
USB Switches
The two USB switches (D+, D-) are bidirectional switches
that can pass rail-to-rail signals. When powered with a 3.3V
supply, these switches have a nominal r_ON of 5.5Ω over the
signal range of 0V to 400mV with a r_ON flatness of 0.5Ω. The
r_ON matching between the D+ and D- switches over this
signal range is only 0.05Ω ensuring minimal impact by the
switches to USB high speed signal transitions. As the signal
level increases, the r_ON resistance increases. At signal level
of 3.3V, the switch resistance is nominally 25Ω.
The USB switches were specifically designed to pass USB
2.0 high-speed (480Mbps) differential signals typically in the
range of 0V to 400mV. They have low capacitance and high
bandwidth to pass the USB high-speed signals with
minimum edge and phase distortion to meet USB 2.0 high
speed signal quality specifications. See Figure 12.
The USB switches can also pass USB full-speed signals
(12Mbps) with minimal distortion and meet all the USB
requirements for USB 2.0 full-speed signaling. See Figure 13
for Full-speed Eye Pattern taken with switch in the signal path.
The maximum signal range for the USB switches is from
-1.5V to V_DD. The signal voltage at D- and D+ should not be
allow to exceed the V_DD voltage rail or go below ground by
more than -1.5V.
The USB switches are active (turned ON) whenever the IN
voltage is ≥ to 1.4V.
ISL54213 Operation
The following will discuss using the ISL54213 in the Typical
Application Block Diagrams shown in Figures 8 and 9.
VDD SUPPLY
The DC power supply connected at VDD (pin 1) provides the
required bias voltage for proper switch operation. The 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 ISL54213 device is determined by the
voltage at the IN pin (pin 2) and the CTRL pin (pin 10).
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 part has three states or modes of
operation. The Audio Mode, USB Mode and Mute 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+ 5.5Ω
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
9
FN6663.0
March 26, 2008