Rainbow Electronics MAX5406 - Manual (Page 22)

MAX5406
Audio Processor with Pushbutton Interface
22 ______________________________________________________________________________________
Subwoofer Output
The subwoofer output of the MAX5406 combines and
filters the left and right inputs for output to a subwoofer.
Choose the capacitor values to set the bandpass filter
to frequencies between 15Hz and 100Hz.
Figure 12 shows the subwoofer output stage configura-
tion. The subwoofer output is a monophonic signal pro-
duced by adding the left and the right input signals.
The amplifier of the subwoofer output stage produces a
bandpass response. Use the following formulas to
determine the cutoff frequencies for the bandpass filter:
where R
_S
is R
LS
or R
RS
and has the nominal value of
13.8k Ω, R
CSUB has the nominal value of 10.6k Ω, and
C C_S is C CLS or C CRS. The external capacitors are as
shown in Figure 12.
Applications Information
Bass Boost
Some simple products may not need a variable bass
tone control. It may be desirable for such products
to have a bass-boost pushbutton. Tie BASSUP and
BASSDN together to provide a bass-boost feature.
When tied together, the bass boost is toggled between
0dB and maximum by pressing BASSUP or BASSDN.
Unequal Source Levels
Audio sources input to the MAX5406 may not have the
same full-scale voltage swings. Use a resistor in series
with the higher voltage swing input source to reduce
the gain for that input.
For example, to reduce the gain by half, add a 10k
Ω
resistor in series with L1_H and R1_H, and a 20k
Ω in
series with L1_L and R1_L.
Chip Information
PROCESS: BiCMOS
f
R S C
f
R C
HIGHPASS
C S
LOWPASS
CSUB CSUB
=
Ч Ч Ч
=
Ч Ч Ч
1
2
1
2
π
π
_
_