isl54405 Intersil Corporation, isl54405 Datasheet - Page 12

• Manufacturer Part Number: isl54405
• Description: Cd/mp3 Quality Stereo 2 1 Multiplexer With Click And Pop Elimination
• Manufacturer: Intersil Corporation

diodes, V
the signal voltages must remain between V
the logic voltage must remain between V
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
below ground or above the V
Logic inputs can be protected by adding a 1kΩ resistor in
series with the logic input (see Figure 8). 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
diodes to the signal pins (as shown in Figure 8) 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.
DD
must be applied before any input signals, and
ON
switch. Connecting Schottky
12
DD
DD
rail.
rail and the logic pin goes
DD
DD
and ground.
and -3V and
ISL54405
.
High-Frequency Performance
In 50Ω systems, the ISL54405 has a -3dB bandwidth of
230MHz (see Figure 29). 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
feedthrough from a switch’s input to its output. Off-Isolation
is the resistance to this feedthrough, while crosstalk
indicates the amount of feedthrough from one switch to
another. Figure 30 details the high Off-Isolation and crosstalk
rejection provided by this part. At 1MHz, Off-Isolation is
about 100dB in 50Ω 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.
OPTIONAL
PROTECTION
RESISTOR
OPTIONAL
SCHOTTKY
DIODE
OPTIONAL
SCHOTTKY
DIODE
FIGURE 8. OVERVOLTAGE PROTECTION
V
LOGIC
INPUT
COM
GND
V
DD
V
NX
June 5, 2008
FN6699.1