9

FN6549.2

November 9, 2009

very consistent over a wide V+ range, and for 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 18 details the high

off-isolation provided by this family. At 1MHz,

of-isolation is about 75dB in 50Ω systems, decreasing

approximately 20dB per decade as frequency

increases. Higher load impedances decrease

off-isolation due to the voltage divider action of the

switch OFF impedance and the load impedance.

Leakage Considerations

ESD protection diodes are internally connected

between each analog-signal pin and both V+ and GND.

One of these diodes conducts if any analog signal

exceeds V+ or GND.

Virtually all the analog leakage current comes from the

ESD diodes to V+ or GND. Although the ESD diodes on

a given signal pin are identical and therefore fairly well

balanced, they are reverse biased differently. Each is

biased by either V+ or GND and the analog signal. This

means their leakages will vary as the signal varies. The

difference in the two diode leakages to the V+ and

GND pins constitutes the analog-signal-path leakage

current. All analog leakage current flows between each

pin and one of the supply terminals, not to the other

switch terminal. This is why both sides of a given

switch can show leakage currents of the same or

opposite polarity. There is no connection between the

analog signal paths and V+ or GND.

FIGURE 10. ON-RESISTANCE vs SUPPLY VOLTAGE vs

SWITCH VOLTAGE

FIGURE 11. ON-RESISTANCE vs SWITCH VOLTAGE

FIGURE 12. ON-RESISTANCE vs SWITCH VOLTAGE

FIGURE 13. ON-RESISTANCE vs SWITCH VOLTAGE

01

2345

0

1

2

3

4

5

6

7

8

V+ = 2.7V

V+ = 3V

V+ = 4.5V

V+ = 5V

1

2

3

4

5

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

V+ = 4.5V

+25°C

+85°C

-40°C

6

2

3

4

5

6

7

8

0

0.5

1.0

1.5

2.0

2.5

V+ = 2.7V

+25°C

+85°C

-40°C

2

3

4

5

6

7

8

9

10

11

12

13

14

0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

V+ = 1.8V

+25°C

+85°C

-40°C

ISL54500