interest are not attenuated. For a typical application, set
f
POLE
equal to or below 20Hz.
Figure 13 shows the frequency response of the circuit
in Figure 12. With RA = 47kΩ, RB = 22kΩ, and CA =
0.33µF, the passband gain is set to 8.8dB.
Layout and Grounding
Proper layout and grounding are essential for optimum
performance. Connect PGND and SGND together at a
single point on the PC board. Connect PV
SS
to SV
SS
and bypass with a 1µF capacitor to PGND. Bypass V
DD
to PGND with a 1µF capacitor. Place the power-supply
bypass capacitor and the charge-pump capacitors as
close to the MAX9723 as possible. Route PGND and all
traces that carry switching transients away from SGND
and the audio signal path. Route digital signal traces
away from the audio signal path. Make traces perpen-
dicular to each other when routing digital signals over
or under audio signals.
The thin QFN package features an exposed paddle
that improves thermal efficiency. Ensure that the
exposed paddle is electrically isolated from PGND,
SGND, and V
DD
. Connect the exposed paddle to
SV
SS
when the board layout dictates that the
exposed paddle cannot be left floating.
MAX9723
Stereo DirectDrive Headphone Amplifier
with BassMax, Volume Control, and I
2
C
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