ISL43120 Datasheet, PDF (8/13 Pages) Intersil Corporation – Low-Voltage, Single Supply, Dual SPST, SPDT Analog Switches

ISL43120, ISL43121, ISL43122, ISL43210
Test Circuits and Waveforms (Continued)
SIGNAL
GENERATOR
V+
C
NO1 or NC1
COM1
50Ω
IN₁
0V or 2.4V
IN₂ ^{0V or VINH}
ANALYZER
COM2
NO2 or NC2
NC
GND
R_L
IMPEDANCE
ANALYZER
NO or NC
V+
C
IN_X 0V or V_INH
COM
GND
FIGURE 6. CROSSTALK TEST CIRCUIT
FIGURE 7. CAPACITANCE TEST CIRCUIT
Detailed Description
The ISL43120–ISL43122 and ISL43210 bidirectional, dual
analog switches offer precise switching capability from a
single 2.7V to 12V supply with low on-resistance (19Ω) and
high speed operation (t_ON = 28ns, t_OFF = 20ns). The devices
are especially well suited to portable battery powered
equipment thanks to the low operating supply voltage (2.7V),
low power consumption (5µW), low leakage currents (100pA
max), and the tiny SOT-23 packaging. High frequency
applications also benefit from the wide bandwidth, and the
very high off isolation and crosstalk rejection.
Supply Sequencing And Overvoltage Protection
With any CMOS device, proper power supply sequencing is
required to protect the device from excessive input currents
which might permanently damage the IC. All I/O pins contain
ESD protection diodes from the pin to V+ and GND (see
Figure 8). To prevent forward biasing these diodes, V+ must
be applied before any input signals, and input signal
voltages must remain between V+ and GND. If these
conditions cannot be guaranteed, then one of the following
two protection methods should be employed.
Logic inputs can easily be protected by adding a 1kΩ
resistor in series with the input (see Figure 8). The resistor
limits the input current below the threshold that produces
permanent damage, and the sub-microamp input current
produces an insignificant voltage drop during normal
operation.
Adding a series resistor to the switch input defeats the
purpose of using a low R_ON switch, so two small signal
diodes can be added in series with the supply pins to provide
overvoltage protection for all pins (see Figure 8). These
additional diodes limit the analog signal from 1V below V+ to
1V above GND. The low leakage current performance is
8
unaffected by this approach, but the switch resistance may
increase, especially at low supply voltages.
OPTIONAL
PROTECTION
RESISTOR
IN_X
V_{NO or NC}
OPTIONAL PROTECTION
DIODE
V+
V_COM
GND
OPTIONAL PROTECTION
DIODE
FIGURE 8. OVERVOLTAGE PROTECTION
Power-Supply Considerations
The ISL43XXX construction is typical of most CMOS analog
switches, except that they have only two supply pins: V+ and
GND. V+ and GND drive the internal CMOS switches and
set their analog voltage limits. Unlike switches with a 13V
maximum supply voltage, the ISL43XXX 15V maximum
supply voltage provides plenty of room for the 10% tolerance
of 12V supplies, as well as room for overshoot and noise
spikes.
The minimum recommended supply voltage is 2.7V. 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.