ISL54065_14 Datasheet, PDF (9/15 Pages) Intersil Corporation – Negative Signal Swing, Sub-ohm, Dual SPDT with Click and Pop Elimination Single Supply Switch with Enable Pin

ISL54065
Detailed Description
The ISL54065 is a bidirectional, dual single pole-double
throw (SPDT) analog switch that offers precise switching
from a single 1.8V to 6.5V supply with low ON-resistance
(0.83Ω) and high speed operation (t_ON = 55ns, t_OFF = 18ns).
The device is especially well suited for portable battery
powered equipment due to its low operating supply voltage
(1.8V), low power consumption (8nA), and a tiny 2.2x1.4mm
µTQFN package. The low ON-resistance and RON flatness
provide very low insertion loss and signal distortion for
applications that require signal switching with minimal
interference by the switch.
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. The ISL54065
contains ESD protection diodes on each pin of the IC (see
Figure 9). These diodes connect to either a +Ring or -Ring
for ESD protection. To prevent forward biasing the ESD
diodes to the +Ring, V+ must be applied before any input
signals, and the input signal voltages must remain between
recommended operating range.
If these conditions cannot be guaranteed, then precautions
must be implemented to prohibit the current and voltage at
the logic pin and signal pins from exceeding the maximum
ratings of the switch. The following two methods can be used
to provided additional protection to limit the current in the
event that the voltage at a logic pin or switch terminal goes
above the V+ rail.
Logic inputs can be protected by adding a 1kΩ resistor in
series with the logic input (see Figure 9). The resistor limits
the input current below the threshold that produces
permanent damage.
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. Connecting external
Schottky diodes to the signal pins will shunt the fault current
to the V+ supply instead of through the internal ESD diodes
thereby protecting the switch. These Schottky diodes must
be sized to handle the expected fault current.
V+
+RING
V_COMx
CLAMP
V_NCx
V_NOx
1kΩ
LOGIC
INPUTS
GND
-RING
FIGURE 9. OVERVOLTAGE PROTECTION
Power-Supply and By-Pass Considerations
The ISL54065 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 5.5V maximum supply voltage, the ISL54065’s 6.5V
maximum supply voltage provides plenty of head room for
the 10% tolerance of 5V supplies due to overshoot and noise
spikes.
The minimum recommended supply voltage is 1.8V. It is
important to note that the input signal range, switching times,
and ON-resistance degrade at lower supply voltages. Refer
to “Electrical Specifications” tables, beginning on page 3,
and “Typical Performance Curves”, beginning on page 11,
for details.
V+ and GND also power the internal logic and level shifters.
The level shifters convert the input logic levels to V+ and
GND signals levels to drive the analog switch gate terminals.
A high frequency decoupling capacitor placed as close to the
V+ and GND pin as possible is recommended for proper
operation of the switch. A value of 0.1µF is highly
recommended.
Negative Signal Swing Capability
The ISL54065 contains circuitry that allows the analog
switch signal to swing below ground. The device has an
analog signal range of 6.5V below V+ up to the V+ rail (see
Figure 16) while maintaining low r_ON performance. For
example, if V+ = 5V, then the analog input signal range is
from -1.5V to +5V. If V+ = 2.7V then the range is from -3.8V
to +2.7V.
Click and Pop Operation
The ISL54065 contains circuitry that prevents audible click
and pop noises that may occur when audio sources are
powered on or off. Single supply audio sources are biased at
a DC offset that can generate transients during power on/off.
A DC blocking capacitor is needed to remove the DC bias at
the speaker load. For 32Ω headphones, a 220µF capacitor is
typically used to preserve the audio bandwidth. The power
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FN6583.2
November 3, 2009