7

FN6379.0

September 29, 2006

Detailed Description

The ISL54057 analog switch offer precise switching

capability from a single 1.6V to 3.6V supply with low

on-resistance (0.41

Ω) and high speed operation

suited to portable battery powered equipment thanks to the

low operating supply voltage (1.6V), low power consumption

(0.17

µW), low leakage currents (60nA max) , and the tiny

flatness provide very low insertion loss and distortion to

applications that require signal reproduction.

Supply Sequencing And Overvoltage Protection

With any CMOS device, proper power supply sequencing is

required to protect the device from excessive input currents

which might permanently damage the IC. All I/O pins contain

ESD protection diodes from the pin to V+ and to GND (see

Figure 7). To prevent forward biasing these diodes, V+ must

be applied before any input signals, and the input signal

voltages must remain between V+ and GND.

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 or logic pin goes below

ground or above the V+ rail.

Logic inputs can be protected by adding a 1k

Ω resistor in

series with the logic input (see Figure 7). 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

diodes to the signal pins as shown in Figure 7 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.

FIGURE 5. CROSSTALK TEST CIRCUIT

FIGURE 6. CAPACITANCE TEST CIRCUIT

0V or V+

ANALYZER

SIGNAL

GENERATOR

GND

ADD1

50

Ω

N.C.

V+

C

Crosstalk is measured between adjacent channels with one channel

ON and the other channel OFF.

Signal direction through switch is reversed and worst case values

are recorded.

ADD0

Channel

Select

INH

GND

Ax or Bx

COMA or COMB

ADD1

IMPEDANCE

ANALYZER

0V or V+

V+

C

ADD0

Channel

Select

INH

FIGURE 7. OVERVOLTAGE PROTECTION

GND

Ax or Bx

V+

INH

OPTIONAL

PROTECTION

RESISTOR

OPTIONAL

SCHOTTKY

DIODE

OPTIONAL

SCHOTTKY

DIODE

or

ISL54057