ISL84516IB データシートの表示（PDF） - Renesas Electronics
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ISL84516IB Datasheet PDF : 10 Pages
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ISL84516, ISL84517
approach, but the switch resistance may increase, especially
at low supply voltage.
OPTIONAL
PROTECTION
RESISTOR IN
VNO or NC
OPTIONAL PROTECTION
DIODE
V+
VCOM
V-
OPTIONAL PROTECTION
DIODE
FIGURE 6. OVERVOLTAGE PROTECTION
Power-Supply Considerations
The ISL8451X construction is typical of most CMOS analog
switches, except that there are only two supply pins: V+ and V-
. The power supplies need not be symmetrical for useful
operation. As long as the total supply voltage (V+ to V-,
including supply tolerances, overshoot, and noise spikes) is
less than the15V maximum supply rating, and the digital input
switching point remains reasonable (see “Logic-Level
Thresholds” section), the ISL84516, ISL84517 function well.
The 15V maximum supply rating provides the designer of 12V
systems much greater flexibility than switches with a 13V
maximum supply voltage.
The minimum recommended supply voltage is 1.5V. It is
important to note that the input signal range, switching times,
and on-resistance degrade at lower supply voltages, and the
digital input VIL becomes negative at VS 2V. Refer to the
“Typical Performance” curves for details.
V+ and V- 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 V- signals to drive the analog switch
gate terminals.
This family of switches is not recommended for single supply
applications. For single supply, similar performance, pin
compatible, TTL compatible versions of these switches, see
the ISL84514, ISL84515 data sheet.
Logic-Level Thresholds
Due to the lack of a GND pin, the switching point of the digital
input is referenced predominantly to V+. The digital input is
CMOS compatible at 5V supplies, and is TTL compatible for
3.3V supplies. For other supply combinations refer to Figure
11.
The switching point has a very low temperature sensitivity, and
changes by only 100mV from 85oC to -40oC, regardless of
supply voltage.
High-Frequency Performance
In 5systems, signal response is reasonably flat to 30MHz,
with a -3dB bandwidth of nearly 400MHz (see Figure 13).
Figure 13 also illustrates that 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 14 details the high
OFF Isolation provided by this family. At 10MHz, OFF Isolation
is about 50dB in 5systems, decreasing approximately 20dB
per decade as frequency increases. Higher load impedances
decrease OFF Isolation 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 V-. One of
these diodes conducts if any analog signal exceeds V+ or
V-.
Virtually all the analog leakage current comes from the ESD
diodes to V+ or V-. 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 V-
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 V- 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 V-.
FN6030 Rev.4.00
May 19, 2005
Page 6 of 10
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