ISL54054_0709 Datasheet, PDF (8/12 Pages) Intersil Corporation – Ultra Low ON-Resistance, Low Voltage, Single Supply, Single SPST/1:2 Distribution Analog Switch

ISL54054, ISL54055
Power-Supply Considerations
The construction of the ISL54054 and the ISL54055 is
typical of most single supply CMOS analog switches in that
they have two supply pins: V+ and GND. V+ and GND drive
the internal CMOS switches and set their analog voltage
limits. Unlike switches with a 4.5V maximum supply voltage,
the ISL54054 and the ISL54055’s 5.5V maximum supply
voltage provides plenty of room for the 10% tolerance of
4.5V supplies, as well as room for overshoot and noise
spikes.
The minimum recommended supply voltage is 1.8V. It is
important to note that the input signal range, switching times,
and on-resistance degrade at lower supply voltages. Refer
to the “Electrical Specifications” tables starting on page 3
and “Typical Performance Curves” on page 8 for details.
V+ and GND also power the internal logic and level shiftier.
The level shiftier converts the input logic levels to switched
V+ and GND signals to drive the analog switch gate
terminals.
This family of switches cannot be operated with bipolar
supplies, because the input switching point becomes
negative in this configuration.
Logic-Level Thresholds
This switch family is 1.8V logic compatible (0.5V and 1.4V)
over a supply range of 2.5V to 5V (see Figure 19). At 5V the
V_IH level is about 1.38V. This is still below the 1.8V CMOS
guaranteed high output minimum level of 1.4V, but noise
margin is reduced. At 1.8V operation the V_IL level is around
0.1V and can only be used in 1.8V applications with minimal
ground bounce.
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, the ISL54054 and the ISL54055 have a -
3dB bandwidth of 72MHz with Nx pins connected and
138MHz for a single Nx input (see Figure 20). 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 feedthrough. Figure 21 details the high
off isolation rejection provided by this family. At 100kHz, off
isolation in 50Ω systems is about 74dB with Nx pins
connected and 83dB with a single Nx input, decreasing
approximately 20dB per decade as frequency increases.
Higher load impedances decrease off isolation 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 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.
Typical Performance Curves T_A = +25°C, Unless Otherwise Specified
1.2
1.4
I_COM = 100mA
V+ = 1.8V
1.1
I_COM = 100mA
1.2
1.0
0.9
V+ = 1.8V
0.8
1.0
+85°C
0.7
0.6
0.5
V+ = 2.7V
0.4
V+ = 4.5V
V+ = 3V
0.3
V+ = 5V
0.2
0
1
2
3
4
5
V_COM (V)
FIGURE 7. ON-RESISTANCE vs SUPPLY VOLTAGE vs
SWITCH VOLTAGE (NX PINS CONNECTED)
0.8
+25°C
0.6
-40°C
0.4
0.2
0
0.5
1.0
V_COM (V)
1.5
1.8
FIGURE 8. ON-RESISTANCE vs SWITCH VOLTAGE
(NX PINS CONNECTED)
8
FN6461.1
September 25, 2007