7

FN6128.2

September 13, 2006

Detailed Description

The ISL8484 is a bidirectional, dual single pole/double throw

(SPDT) analog switch that offers precise switching capability

from a single 1.65V to 4.5V supply with low on-resistance

(0.23

The device is especially well suited for portable battery

powered equipment due to its low operating supply voltage

(1.65V), low power consumption (4.5

µW max), low leakage

currents (110nA max), and the tiny DFN and MSOP

packages. The ultra low on-resistance and Ron 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 8). 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 one of the following

two protection methods should be employed.

Logic inputs can easily be protected by adding a 1kW

resistor in series with the 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

diodes can be added in series with the supply pins to provide

FIGURE 4. OFF ISOLATION TEST CIRCUIT

FIGURE 6. CROSSTALK TEST CIRCUIT

FIGURE 7. CAPACITANCE TEST CIRCUIT

ANALYZER

SIGNAL

GENERATOR

V+

C

0V OR V+

NO OR NC

COM

IN

GND

Signal direction through switch is reversed, worst case values

are recorded. Repeat test for all switches.

V+

C

0V OR V+

NO OR NC

COM

IN

GND

100mA

Repeat test for all switches.

0V or V+

ANALYZER

V+

C

NO OR NC

SIGNAL

GENERATOR

GND

COM

50

Ω

N.C.

COM

NC or NO

Signal direction through switch is reversed, worst case values

are recorded. Repeat test for all switches.

V+

C

GND

NO OR NC

COM

IN

IMPEDANCE

ANALYZER

0V OR V+

Repeat test for all switches.

ISL8484