54405IVZ 查看數據表（PDF） - Intersil

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54405IVZ

CD/MP3 Quality Stereo 2:1 Multiplexer with Click and Pop Elimination

Intersil 

ISL54405

diodes, VDD must be applied before any input signals, and

the signal voltages must remain between VDD and -3V and

the logic voltage must remain between VDD 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 VDD rail and the logic pin goes

below ground or above the VDD rail.

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 rON switch. Connecting Schottky

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.

.

OPTIONAL

SCHOTTKY

DIODE

OPTIONAL

PROTECTION

RESISTOR

LOGIC

INPUT

VCOM

VDD

VNX

OPTIONAL

SCHOTTKY

DIODE

GND

FIGURE 8. OVERVOLTAGE PROTECTION

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.

12

FN6699.1

June 5, 2008

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