ISL54405_14 Datasheet, PDF (12/20 Pages) Intersil Corporation – CD/MP3 Quality Stereo 2:1 Multiplexer with Click and Pop Elimination

ISL54405
V_DD must be applied before any input signals, and the signal
voltages must remain between V_DD and -3V and the logic
voltage must remain between V_DD and ground.
If these conditions cannot be guaranteed, then precautions
must be implemented to prohibit the current and voltage at
the logic pin and signal pins from exceeding the maximum
ratings of the switch. The following two methods can be used
to provided additional protection to limit the current in the
event that the voltage at a signal pin goes below ground by
more than -3V or above the V_DD rail and the logic pin goes
below ground or above the V_DD rail.
Logic inputs can be protected by adding a 1k resistor in
series with the logic input (see Figure 9). The resistor limits the
input current below the threshold that produces permanent
damage, and the sub-microamp input current produces an
insignificant voltage drop during normal operation.
This method is not acceptable for the signal path inputs.
Adding a series resistor to the switch input defeats the purpose
of using a low r_ON switch. Connecting Schottky diodes to the
signal pins, as shown in Figure 9 will shunt the fault current to
the supply or to ground thereby protecting the switch. These
Schottky diodes must be sized to handle the expected fault
current and to clamp when the voltage reaches the
overvoltage limit.
.
OPTIONAL
SCHOTTKY
DIODE
OPTIONAL
PROTECTION
RESISTOR
LOGIC
INPUT
V_COM
V_DD
V_NX
OPTIONAL
SCHOTTKY
DIODE
GND
FIGURE 9. OVERVOLTAGE PROTECTION
High-Frequency Performance
In 50 systems, the ISL54405 has a -3dB bandwidth of
230MHz (see Figure 30). The frequency response is very
consistent over varying analog signal levels.
An OFF-switch acts like a capacitor and passes higher
frequencies with less attenuation, resulting in signal
feed-through from a switch’s input to its output. OFF-Isolation
is the resistance to this feed-through, while crosstalk indicates
the amount of feed-through from one switch to another.
Figure 31 details the high OFF-Isolation and crosstalk rejection
provided by this part. At 1MHz, Off-Isolation is about 100dB in
50 systems, decreasing approximately 20dB per decade as
frequency increases. Higher load impedances decrease
OFF-Isolation and crosstalk rejection due to the voltage divider
action of the switch off impedance and the load impedance.
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FN6699.2
May 6, 2014