Max5406 audio processor with pushbutton interface – Rainbow Electronics MAX5406 User Manual
Page 21
MAX5406
Audio Processor with Pushbutton Interface
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21
Pseudostereo
Pseudostereo creates a sound approximating stereo
from a monophonic signal. Use the equations for pseu-
dostereo response calculations:
Connect a pseudostereo network (F
L(S)
and F
R(S)
) as
shown in Figure 10 to filter and delay the LPR signal
and create the pseudo signal.
Click/Pop Suppression
The click/pop suppression feature reduces the audible
noise (clicks and pops) that results from wiper transi-
tions. The MAX5406 minimizes this noise by allowing
the wiper position changes only when the potential
across the pot is zero. Thus, the wiper changes posi-
tion only when the voltage at L_ is the same as the volt-
age at the corresponding H_. Each wiper has its own
suppression and timeout circuitry (see Figure 11a). The
MAX5406 changes wiper position after 32ms or when
high = low, whichever occurs first (see Figure 11b).
Power-On Reset
The MAX5406 initiates power-on reset when V
LOGIC
falls below 2.2V and returns to normal operation when
V
LOGIC
= +2.7V. A power-on reset places the volume in
the mute (-90dB) state and volume wipers gradually
move to -20dB over a period of 0.7s in 2dB steps if no
zero-crossing event is detected. All other controls
remain in the 0dB position.
Shutdown (
SHDN
)
The MAX5406 stores the current wiper setting of each
potentiometer in shutdown mode. The wipers move to
the mute position to minimize the signal out of LOUT
and ROUT. Returning from shutdown mode restores all
wipers to their previous settings. Button presses in
shutdown are ignored.
Mute Function (
MUTE
)
The MAX5406 features a mute function that sets the
volume typically 90dB attenuation relative to full scale.
Successive pulses on MUTE toggle its setting.
Activating the mute function forces all wipers to the low
side of the potentiometer chain. Deactivating the mute
function returns the wipers to their previous settings.
MUTE is internally pulled high with a 50k
Ω resistor
to V
LOGIC
.
Multiple Button Pushes
The MAX5406 ignores simultaneous presses of two or
more buttons. Pushing more than one button at the
same time does not change the state of the wipers.
Additionally, further key presses are ignored for 50ms
after all keys have been released. The MAX5406 does not
respond to any logic input until the blocking period ends.
Bias Generator
The MAX5406 generates a midrail, (V
DD
+ V
SS
) / 2 bias
voltage, for use with the input amplifiers.
For normal single-supply operation and single-ended
signals, connect R1_L, L1_L, R2_L, and L2_L to V
BIAS
and V
SS
to ground.
Enable the V
BIAS
generator by connecting CMSNS to V
SS
or leave CMSNS unconnected. Disable the V
BIAS
genera-
tor by forcing CMSNS to V
DD
. For proper operation, do not
use V
BIAS
to power other circuitry.
where
L
R
are the signals at LPR
IN
IN
+
⎛
⎝⎜
⎞
⎠⎟
4
.
LOUT L
F
L
R
ROUT R
F
L
R
IN
L S
IN
IN
IN
R S
IN
IN
=
+
Ч
+
=
Ч
+
( )
( )
(
)
(
)
4
4
-
LEFT CHANNEL
INPUT
RIGHT CHANNEL
INPUT
CLSP
CLSN
CSUB
C
CSUB
SUBOUT
CRSN
CRSP
C
CRS
C
CLS
R
RS
R
LS
R
SUB
V
BIAS
Figure 12. Subwoofer Output Stage