ISL54217_09 Datasheet, PDF (10/21 Pages) Intersil Corporation – USB 2.0 High-Speed x 2Channels/Stereo Audio Dual SP3T (Dual 3-to-1 Multiplexer)

ISL54217
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 ±1V (0.707Vrms) 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 (<0.05% 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 and 26 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
minimum edge and phase distortion to meet USB 2.0 signal
quality specifications. See Figures 27 and 28 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
29 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_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 -1V for normal operation.
However in the event that the USB 5.25V V_BUS voltage were
shorted to one or both of the COM pins, the ISL54217 has
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 5.25V while
the V_DD supply voltage is in the range of 0V to 4.6V. This
fault condition causes no stress to the IC. In addition, when
V_DD is at 0V (ground) all switches are OFF and the fault
voltage is isolated from the other side of the switch. When
V_DD is in the 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 4MΩ
resistors to ground and can be tri-stated or left floating.
The C1 pin and C0 pin can be driven with a voltage that is
higher than the V_DD supply voltage. They can be driven up
to 5.25V with the V_DD supply in the range of 2.7V to 4.6V.
Driving the logic higher than the supply rail will cause the
logic current to increase. With V_DD = 2.7V and V_LOGIC =
5.25V, I_LOGIC current is approximately 5.5µA.
10
FN6817.3
May 4, 2009