ISL43110, ISL43111
7
FN6028.4
June 27, 2014
Submit Document Feedback
Detailed Description
The ISL43110 and ISL43111 analog switches offer precise
switching capability from a single 2.4V to 12V supply with low
ON-resistance and high speed operation. The devices are
especially well suited to portable battery powered equipment
thanks to the low operating supply voltage (2.4V), low power
consumption (5µW), low leakage currents (1nA max), and the
tiny SOT-23 packaging. High frequency applications also benefit
from the wide bandwidth, and the very high off-isolation.
Supply Sequencing And Overvoltage
Protection
As 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 to GND
(see Figure 6
). 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 1k resistor
in series with the input (see Figure 6
). 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 6
). These additional diodes
limit the analog signal from 1V below V+ to 1V above GND. The
low leakage current performance is unaffected by this
approach, but the switch resistance may increase, especially
at low supply voltages.
Power-Supply Considerations
The ISL4311X construction is typical of most CMOS analog
switches, except that there are only two supply pins: V+ and
GND. Unlike switches with a 13V maximum supply voltage, the
ISL4311X 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 2.4V. 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 on page 3
and “Typical
Performance Curves” on page 8 for details.
V+ and GND power the internal CMOS switches and set their
analog voltage limits. These supplies also power the internal
logic and level shifters. The level shifters convert 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. For a ±5V single SPST switch, see the
ISL43112 and ISL43113 data sheet.
FIGURE 5. CAPACITANCE TEST CIRCUIT
Test Circuits and Waveforms (Continued)
V+
GND
NO or NC
COM
IN
IMPEDANCE
ANALYZER
0V or V+
FIGURE 6. OVERVOLTAGE PROTECTION
GND
V
COM
V
NO or NC
OPTIONAL PROTECTION
V+
IN
DIODE
OPTIONAL PROTECTION
DIODE
OPTIONAL
PROTECTION
RESISTOR
