ISL43L420_14 Datasheet, PDF (8/13 Pages) Intersil Corporation – Ultra Low ON-Resistance, +1.1V to +4.5V Single Supply, Quad SPDT Analog Switch

ISL43L420
Test Circuits and Waveforms (Continued)
V+
C
SIGNAL
GENERATOR
NO or NC
COM
50Ω
IN₁
0V or V+
ANALYZER
R_L
COM
NC or NO
GND
N.C.
IMPEDANCE
ANALYZER
NO or NC
V+
C
IN 0V or V+
COM
GND
FIGURE 6. CROSSTALK TEST CIRCUIT
FIGURE 7. CAPACITANCE TEST CIRCUIT
Detailed Description
The ISL43L420 is a bidirectional, quad single pole/double
throw (SPDT) analog switch that offers precise switching
capability from a single 1.1V to 4.5V supply with low on-
resistance (0.24Ω) and high speed operation (t_ON = 8ns,
t_OFF = 5ns). The device is especially well suited for portable
battery powered equipment due to its low operating supply
voltage (1.1V), low power consumption (2.7µW max), low
leakage currents (150nA max), and the tiny QFN package.
The ultra low on-resistance and R_ON flatness provide very low
insertion loss and distortion to applications that require signal
reproduction.
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 to GND (See
Figure 8). To prevent forward biasing these diodes, V+ must
be applied before any input signals, and the 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.
This method is not acceptable for the signal path inputs.
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
8
1V above GND. The low leakage current performance is
unaffected by this approach, but the switch signal range is
reduced and the 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 ISL43L420 construction 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 4V maximum supply voltage, the ISL43L420 4.7V
maximum supply voltage provides plenty of room for the
10% tolerance of 4.3V supplies, as well as room for
overshoot and noise spikes.
The minimum recommended supply voltage is 1.1V. 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.
FN6098.1