ISL54503 Datasheet, PDF (9/13 Pages) Intersil Corporation – +1.8V to +5.5V, 2.5OHM, Single SPDT Analog Switch

ISL54503
An OFF switch behaves like a capacitor and passes
higher frequencies with less attenuation, resulting in
signal feed-through from a switch’s input to output.
Off-isolation is the resistance of this signal
feed-through. Figure 18 details the high off-isolation
provided by the ISL54503. At 1MHz, off-isolation is
about 70dB 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.
9
FN6551.2
October 26, 2009