ISL54217 Intersil Corporation, ISL54217 Datasheet - Page 10

• Manufacturer Part Number: ISL54217
• Description: USB 2.0 High-Speed x 2Channels/Stereo Audio Dual SP3T
• Manufacturer: Intersil Corporation

to combine the stereo audio and USB data channels into a
single shared connector, thereby saving space and
component cost. The Typical application block diagram of
this functionality is previously shown.
The ISL54217 contains two logic control pins (C1 and C0)
that determine the state of the device. The part has the
following five states or modes of operation: All SWITCHES
OFF; USB1; USB2; Audio; and Audio Mute. These states
are discussed in detail in “Logic Control” on page 10.
A detailed description of the various types of switches are
provided in “Audio Switches” beginning on page 10.
Audio Switches
The two audio switches (L, R) are 2.3Ω switches that can
pass signals that swing below ground.
Over a signal range of
these switches have an extremely low r
variation. They can pass ground referenced audio signals with
very low distortion (<0.05% THD+N) when delivering 15.6mW
into a 32Ω headphone speaker load. See Figures 20, 21, 22,
23 and 24 THD+N performance curves.
Crosstalk between the L and R audio switches over the
frequency range of 20Hz to 20kHz when driving a 32Ω load
is < -88dB. These switches have excellent off-isolation >
105dB over the audio band when connected to 32Ω loads
and 77dB when connected to 20kΩ loads (In Audio Mute
mode). See Figures 25, 26, and 27 in “Typical Performance
Curves” section beginning on page 12.
The audio drivers should be connected at the L and R side of
the switch (pins 2 and 3) and the speaker loads should be
connected at the COM side of the switch (pins 7 and 8).
The switches have click and pop circuitry on the L and R
side that is activated when the part comes out of Audio mode
by taking the C1 and C0 logic pins low (All OFF mode). The
ISL54217 should be put in this mode before powering down
or powering up of the audio CODEC drivers. In this mode the
audio, USB1, USB2 switches will be OPEN (OFF) and the
audio click and pop circuitry will be ON. The high off-isolation
of the audio switches along with the click and pop circuitry
will isolate the transients generated during power-up and
power down of the audio CODECs from getting through to
the headphones thus eliminating click and pop noise in the
headphones. See the “AC Coupled click and pop operation”
on page 12.
The audio switches are active (turned ON) whenever the C1
and C0 logic pins are logic “1” (High).
USB Switches
The four USB switches (1D+, 1D-, 2D+, 2D-) are 6.2Ω
bidirectional switches that were specifically designed to pass
high-speed USB differential data signals in the range of 0V
to 400mV. The switches have low capacitance and high
bandwidth to pass USB high-speed signals (480Mbps) with
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±
1V (0.707Vrms) with VDD > 2.7V,
10
ON
resistance
ISL54217
minimum edge and phase distortion to meet USB 2.0 signal
quality specifications. See Figures 28 and 29 for High-speed
Eye Pattern taken with switch in the signal path.
These switches can also swing rail to rail and pass USB
full-speed signals (12Mbps) with minimal distortion. See Figure
30 for Full-speed Eye Pattern taken with switch in the signal
path.
The maximum normal operating signal range for the USB
switches is from -1V to V
should not be allow to exceed the V
below ground by more than -1V for normal operation.
However in the event that the USB 5.25V V
shorted to one or both of the COM pins, the ISL54217 has
special fault protection circuitry to prevent damage to the
ISL54217 part. The fault circuitry allows the signal pins
(COM-, COM+, 1D-, 1D+, 2D-, 2D+, L and R) to be driven up
to 5.5V while the V
4.6V. In this condition the part draws < 1µA of current and
causes no stress to the IC. In addition, when V
(ground) all switches are OFF and the fault voltage is
isolated from the other side of the switch. When V
range of 2.7V to 4.6V the fault voltage will pass through to
the output of an active switch channel. Note: During the fault
condition normal operation is not guaranteed until the fault
condition is removed.
The USB (1D+ and 1D-) switches are active (turned ON)
whenever the C1 is logic “0” (Low) and C0 is logic “1” (High).
The USB (2D+ and 2D-) switches are active (turned ON)
whenever the C1 is logic “1” (High) and C0 is logic “0” (Low)
provided the last state was not the Audio or Audio Mute
state.
ISL54217 Operation
The discussion that follows will discuss using the ISL54217 in
the “Block Diagram” on page 9.
LOGIC CONTROL
The state of the ISL54217 device is determined by the
voltage at the C1 pin (pin 9) and the C0 pin (pin 10). The part
has five states or modes of operation. The All SWITCHES
OFF mode, USB1 mode, USB2 mode, Audio mode and
Audio Mute mode. Refer to “Truth Table” on page 3 and
“State Diagram” on page 2 of data sheet.
The C1 pin and C0 pin are internally pulled low through 4M
resistors to ground and can be tri-stated or left floating.
Logic Control Voltage Levels
With VDD in the range of 2.7V to 3.6V the logic levels are:
C1, C0 = Logic “0” (Low) when
C1, C0 = Logic “1” (High) when
ALL SWITCHES OFF Mode
If the C1 pin = Logic “0” and C0 pin = Logic “0” the part will
be in the ALL SWITCHES OFF mode. In this mode the 2D-
DD
supply voltage is in the range of 0V to
DD
. The signal voltage at D- and D+
≤
≥
0.5V or Floating.
1.4V
DD
voltage rail or go
BUS
DD
December 11, 2008
voltage were
DD
is at 0V
is in the
FN6817.0
Ω