ISL43681_06 Datasheet, PDF (14/17 Pages) Intersil Corporation – Low-Voltage, Single and Dual Supply, 8 to 1 Multiplexer and Differential 4 to 1 Multiplexer

ISL43681, ISL43741
recommended supply voltage is 2V or ±2V. It is important to
note that the input signal range, switching times, and on-
resistance degrade at lower supply voltages. Refer to the
electrical specification tables and Typical Performance
curves for details.
V+ and GND power the internal logic (thus setting the digital
switching point) and level shifters. The level shifters convert
the logic levels to switched V+ and V- signals to drive the
analog switch gate terminals.
Logic-Level Thresholds
V+ and GND power the internal logic stages, so V- has no
affect on logic thresholds. This switch family is TTL
compatible (0.8V and 2.4V) over a V+ supply range of 2.7V
to 10V. At 12V the V_IH level is about 3.3V. This is still below
the CMOS guaranteed high output minimum level of 4V, but
noise margin is reduced. For best results with a 12V supply,
use a logic family that provides a V_OH greater than 4V.
The digital input stages draw supply current whenever the
digital input voltage is not at one of the supply rails. Driving
the digital input signals from GND to V+ with a fast transition
time minimizes power dissipation.
High-Frequency Performance
In 50Ω systems, signal response is reasonably flat even past
100MHz (see Figures 18 and 19). Figures 18 and 19 also
illustrates that 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 feed
through from a switch’s input to its output. Off Isolation is the
resistance to this feed through, while Crosstalk indicates the
amount of feed through from one switch to another. Figure
20 details the high Off Isolation and Crosstalk rejection
provided by this family. At 10MHz, Off Isolation is about
55dB 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.
Leakage Considerations
Reverse ESD protection diodes are internally connected
between each analog-signal pin and both V+ and V-. One
of these diodes conducts if any analog signal exceeds V+
or V-.
Virtually all the analog leakage current comes from the ESD
diodes to V+ or V-. 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 V- 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 V- 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 GND.
Typical Performance Curves T_A = 25°C, Unless Otherwise Specified
70
V- = -5V
V_COM = (V+) - 1V
60
I_COM = 1mA
50
85°C
40
25°C
30
-40°C
20
400
V- = 0V
300
200
85°C
25°C
100
-40°C
0
2345
678
V+ (V)
9 10 11 12
FIGURE 10. ON RESISTANCE vs SUPPLY VOLTAGE
120
110
100
I_COM = 1mA
90
80
70
60
50
90
80
70
85°C
60
50
25°C
40
-40°C
30
60
50 _25°C
85°C
40
85°C
V_S = ±2V
25°C
-40°C
V_S = ±3V
V_S = ±5V
30 _-40°C
20
-5 -4 -3 -2 -1 0 1 2 3 4 5
V_COM (V)
FIGURE 11. ON RESISTANCE vs SWITCH VOLTAGE
14
FN6053.3
March 13, 2006