ISL54066 Datasheet, PDF (9/14 Pages) Intersil Corporation – 1.8V to +6.5V, High Off-Isolation, Dual SPST Analog Switch

ISL54066
V+ and GND also power the internal logic and level shifters.
The level shifters convert the input logic levels to V+ and
GND signals levels to drive the analog switch gate terminals.
A high frequency decoupling capacitor placed as close to the
V+ and GND pin as possible is recommended for proper
operation of the switch. A value of 0.1µF is highly
recommended.
Negative Signal Capability
The ISL54066 contains circuitry that allows the analog input
signal to swing below ground. The device has an analog signal
range of 6.5V below V+ up to the V+ rail (see Figure 14) while
maintaining low r_ON performance. For example, if V+ = 5V,
then the analog input signal range is from -1.5V to +5V. If
V+ = 2.7V then the range is from -3.8V to +2.7V.
Logic-Level Thresholds
This switch family is 1.8V CMOS compatible (0.45V V_OLMAX
and 1.35V V_OHMIN) over a supply range of 1.8V to 3.3V
(see Figure 16). At 3.3V the V_IL level is 0.5V maximum. This
is still below the 1.8V CMOS guaranteed low output
maximum level of 0.45V, but noise margin is reduced. At
3.3V the V_IH level is 1.4V minimum. While this is above the
1.8V CMOS guaranteed high output minimum of 1.35V
under most operating conditions the switch will recognize
this as a valid logic high.
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. The ISL54066 has been
designed to minimize the supply current whenever the digital
input voltage is not driven to the supply rails (0V to V+). For
example, driving the device with 2.85V logic high while
operating with a 4.2V supply, the device draws only 1µA of
current.
High-Frequency Performance
In 50Ω systems, the ISL54066 has a -3dB bandwidth of
30MHz (see Figure 19). The frequency response is 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 feed-through, while Crosstalk
indicates the amount of feedthrough from one switch to
another. Figure 20 details the high Off-Isolation and
Crosstalk rejection provided by this part. At 1MHz,
Off-Isolation is approximately 70dB in 50Ω systems,
decreasing approximately 40dB per decade as frequency
increases. Crosstalk is approximately -80dB at 1MHz in 50Ω
systems.
Leakage Considerations
Reverse ESD protection diodes are internally connected
between each analog-signal pin, V+ and GND. One of these
diodes conducts if any analog signal exceeds the
recommended analog signal range.
Virtually all the analog switch leakage current comes from
the ESD diodes and reversed biased junctions in the switch
cell. Although the ESD diodes on a given signal pin are
identical and therefore fairly well balanced, they are reverse
biased differently. Each is biased to either the +Ring or -Ring
and the analog input signal. This means their leakages will
vary as the signal varies. The difference in the two diode
leakages to the +Ring or -Ring and the reverse biased
junctions at the internal switch cell constitutes the
analog-signal-path leakage current.
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FN6584.0
February 25, 2009