MAX4991–MAX4994
Analog Signal Levels
The MAX4991–MAX4994 have a very low and stable
R
ON
, 0.3Ω (typ), as the analog input signals are swept
from ground to V
CC
(see
Typical Operating Character-
istics
). These switches are bidirectional, allowing NO_,
NC_, and COM_ to be configured as either inputs or
outputs; however, click-and-pop reduction is only oper-
ational when COM_ is used as the output.
Power-Supply Rejection Ratio
PSRR is the measurement of AC power-supply ripple or
noise that couples to the output. Variations in supply volt-
age corrupt the audio signal due to changes in the R
ON
value by supply modulation. The MAX4991–MAX4994
maintain a 80dB (typ) PSRR across the supply-voltage
range, eliminating any corruption of the audio signal from
supply variations. Therefore, with no audio signal, the
R
ON
variation due to supply-voltage ripple does not con-
tribute to any output signal modulation.
Applications Information
Click-Pop Reduction
The MAX4991/MAX4993 feature a slow switch turn-on
that can reduce click-and-pop noise caused by abrupt
changes in voltage across a speaker. These voltage
changes usually occur when a single-supply audio
amplifier with a DC bias is turned on, causing a spike of
current in the speaker while the coupling capacitor
charges (see the
Typical Operating Circuit
). If the audio
amplifier connected to the unused input is powered up
before the switch position changes, the MAX4991/
MAX4993 reduce the current spike to COM_. The
speaker load must be present so that the current
charging the coupling capacitor has a path to ground.
Layout
Good layout improves performance by decreasing the
amount of stray capacitance and noise. Minimize PCB
trace lengths and resistor leads and place external
components as close as possible to the device.
Power-Supply Sequencing
Caution: Do not exceed the absolute maximum rat-
ings because stresses beyond the listed ratings
may cause permanent damage to the device.
Proper power-supply sequencing is recommended for
all devices. Always apply V
CC
before applying analog
signals especially if the analog signal is not current
limited.
Low R
ON
, Dual-SPDT/Single-DPDT Analog
Switches with Slow Turn-On Time
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