MAX4994 Просмотр технического описания (PDF) - Maxim Integrated

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MAX4994

Low RON, Dual-SPDT/Single-DPDT Analog Switches with Slow Turn-On Time

Maxim Integrated 

Low RON, Dual-SPDT/Single-DPDT Analog

Switches with Slow Turn-On Time

Analog Signal Levels

The MAX4991–MAX4994 have a very low and stable

RON, 0.3Ω (typ), as the analog input signals are swept

from ground to VCC (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 RON

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

RON 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 VCC before applying analog

signals especially if the analog signal is not current

limited.

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