ISL43681 Datasheet, PDF (13/17 Pages) Intersil Corporation – Low-Voltage, Single and Dual Supply, 8 to 1 Multiplexer and Differential 4 to 1 Multiplexer

ISL43681, ISL43741
Test Circuits and Waveforms (Continued)
V+
C
V-
C
SIGNAL
GENERATOR
EN, LE
NO_A or NC_A
COM_A
ADDX
0V or V+
ISL43741
ANALYZER
R_L
COM_B
NO_B or NC_B
GND EN
50Ω
N.C.
IMPEDANCE
ANALYZER
V+
C
V-
C
EN, LE
NO or NC
0V or V+
ADDX
COM
GND EN
FIGURE 7. CROSSTALK TEST CIRCUIT
Detailed Description
The ISL43681 and ISL43741 multiplexers offer precise
switching capability from a bipolar ±2V to ±6V or a single 2V
to 12V supply with low on-resistance (39Ω) and high speed
operation (t_ON = 38ns, t_OFF = 19ns) with dual 5V supplies.
They have an inhibit and inhibit bar pin to simultaneously
open all signal paths. They also have a latch bar pin to lock
in the last switch address.
The devices are especially well suited for applications using
±5V supplies. With ±5V supplies the performance (R_ON,
Leakage, Charge Injection, etc.) is best in class.
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 to V- (see
Figure 9). To prevent forward biasing these diodes, V+ and
V- must be applied before any input signals, and input signal
voltages must remain between V+ and V-. 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 9). 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 applicable 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
13
FIGURE 8. CAPACITANCE TEST CIRCUIT
diodes can be added in series with the supply pins to provide
overvoltage protection for all pins (see Figure 9). These
additional diodes limit the analog signal from 1V below V+ to
1V above V-. The low leakage current performance is
unaffected by this approach, but the switch resistance may
increase, especially at low supply voltages.
OPTIONAL
PROTECTION
RESISTOR
FOR LOGIC
INPUTS
1kΩ _LOGIC
V_{NO or NC}
OPTIONAL PROTECTION
DIODE
V+
V_COM
V-
OPTIONAL PROTECTION
DIODE
FIGURE 9. INPUT OVERVOLTAGE PROTECTION
Power-Supply Considerations
The ISL43681 and ISL43741 construction is typical of most
CMOS analog switches, in that they have three supply pins:
V+, V-, and GND. V+ and V- drive the internal CMOS
switches and set their analog voltage limits, so there are no
connections between the analog signal path and GND.
Unlike switches with a 13V maximum supply voltage, the
ISL43681 and ISL43741 15V maximum supply voltage
provides plenty of room for the 10% tolerance of 12V
supplies (±6V or 12V single supply), as well as room for
overshoot and noise spikes.
This family of switches performs equally well when operated
with bipolar or single voltage supplies.The minimum