isl54406 Intersil Corporation, isl54406 Datasheet - Page 8

• Manufacturer Part Number: isl54406
• Description: Stereo Click And Pop Eliminator With Audio Muting
• Manufacturer: Intersil Corporation

Logic Control Voltage Levels:
SEL1 and SEL2 = Logic “0” (Low) when
SEL1 and SEL2 = Logic “1” (High) when
Audio Playback Mode
If the SEL1 and SEL2 pins are Logic “1”, the device will be in
the Audio Playback mode. In Audio Playback mode the LIN
(left) and RIN (right) 2.5Ω audio switches are connected to
LOUT and ROUT respectively, and the audio Click and Pop
circuitry is inactive (high impedance). When headphones are
connected to the LOUT and ROUT outputs of the ISL54406,
the audio source drives the headphones with low distortion
audio.
Audio Mute Mode
If SEL1 is Logic “0” and SEL2 is Logic “1”, the device will be
in the Audio Mute Mode. In Audio Mute Mode the audio
switches are OFF (high impedance), the audio Click and
Pop shunt circuitry is OFF (high impedance), and the LOUT
and ROUT pins are shorted through 6Ω resistors to ground.
Off Isolation performance in Audio Mute Mode gives a 110
dB signal reduction across a 32Ω load when driving with a
0.707V
Click and Pop Mode
Note: Click and Pop Mode should not be used for audio
muting applications. In Click and Pop Mode, a low
impedance (35Ω) path to ground at the LIN/RIN inputs will
degrade Off Isolation performance (see Figure 14).
If SEL1 is Logic “1” and SEL2 is Logic “0”, the device will go
into Click and Pop Mode. This mode is optimal when
powering up or down the audio sources. In Click and Pop
Mode the audio in-line 2.5Ω switches are OFF (high
impedance). The LOUT and ROUT pins are shorted through
6Ω resistors to ground and the LIN and RIN are shunted
through 35Ω resistors to ground (Click and Pop circuitry is
active).
Before powering down or powering up of the audio source
drivers, the ISL54406 should be put in the Click and Pop
Mode. In Click and Pop Mode, transients generated at the
LIN and RIN pins due to a DC step voltage at the audio
drivers will not pass through the ISL54406 audio switches,
preventing Click and Pop noise to the load.
Shutdown Mode
If SEL1 and SEL2 pins are Logic “0”, the device will enter a
low powered Shutdown (SHDN) Mode. In SHDN, the audio
switches are OFF, the 6Ω path is high impedance, the Click
and Pop circuitry is inactive, and the device will draw a
typical supply current of 5nA.
Note: When the logic inputs are floated, the ISL54406 will
automatically be placed in SHDN mode due to the internal
4MΩ pull down resistors on the logic pins.
Note: In Shutdown Mode, the Off-Isolation of the audio
switch degrades in performance compared to Audio Mute
RMS
signal at the switch input.
8
≤
≥
0.5V or Floating.
1.4V
ISL54406
Mode. In SHDN, the negative charge pumps that permit the
signal to swing below ground are turned off to reduce power
consumption, thus any negative signal swing at the LIN and
RIN will appear at the LOUT and ROUT pins. The device
should not be placed into SHDN when the source is still
active or for high Off-Isolation performance.
CLICK AND POP OPERATION
Single supply audio sources are biased at a DC offset that
generates transients during power on/off of the source. This
DC transient is coupled into the load through a blocking
capacitor (see “Application Block Diagram” on page 7).
When the source is off and suddenly turned on with a DC
offset, the capacitor will develop a voltage across it that is
equal to the DC offset. If the switch is in Audio mode when
this occurs, a transient discharge will occur in the speaker,
generating a Click and Pop noise.
Proper elimination of Click and Pop transients requires that
the ISL54406 be placed in Click and Pop Mode before the
audio source is turned on or off. This allows any transients
generated by the source to be discharged through the Click
and Pop circuitry first. With a typical DC blocking capacitor of
220µF and the Click and Pop circuitry designed to have a
resistance of 35Ω, allowing a 100ms dead-time for
discharging a transient before placing the switch in Audio
mode will eliminate the DC transient generated by the
blocking capacitor.
Note: The ISL54406 should not be brought into Audio
Playback Mode directly from Shutdown Mode and vice
versa. A DC transient may occur at the LOUT/ROUT pins
when brought from Shutdown directly to Audio Playback
mode. The recommended procedure is to place the
ISL54406 into Mute mode for at least 100ms when entering
or leaving Audio Playback mode.
Power supply considerations
The power supply connected at V
power to the ISL54406 part. In a typical application V
be in the range of +2.7V to +5.0V and will be connected to
the battery or LDO of the MP3 player or cellphone. A 0.1µF
local decoupling capacitor should be placed near the V
pin of the IC to eliminate power supply transients.
Before power-up and power-down of the ISL54406 part, the
SEL1 and SEL2 logic control pins should be driven to Logic
“0” or left floating. In a high impedance state, 4MΩ internal
pull down resistors on the SEL1 and SEL2 pins will set the
ISL54406 logic pins to “0”. This will put the switch in the
SHDN state which turns all switches OFF and deactivates
the Click and Pop circuitry which will minimize power supply
currents and increase battery life.
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May 28, 2008
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