Datasheet

To suppress this noise, and to provide a 2V
RMS
stan-
dard audio output level from a single 5V supply, the
MAX9724A can be configured as a line driver and
active lowpass filter. Figure 5 shows the MAX9724A
connected as 2-pole Rauch/multiple feedback filter with
a passband gain of 6dB and a -3dB (below passband)
cutoff frequency of approximately 27kHz (see Figure 6
for the Gain vs. Frequency plot).
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. Place the power-sup-
ply bypass capacitor and the charge-pump hold
capacitor as close to the MAX9724 as possible. Route
PGND and all traces that carry switching transients
away from SGND and the audio signal path. 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
only
when the board layout dictates that the exposed
paddle cannot be left floating.
UCSP Applications Information
For the latest application details on UCSP construction,
dimensions, tape carrier information, printed circuit
board techniques, bump-pad layout, and recommend-
ed reflow temperature profile, as well as the latest infor-
mation on reliability testing results, refer to the
Application Note UCSP—A Wafer-Level Chip-Scale
Package available on Maxim’s website at www.maxim-
ic.com/ucsp.
MAX9724A/MAX9724B
60mW, DirectDrive, Stereo Headphone Amplifier
with Low RF Susceptibility and Shutdown
14 ______________________________________________________________________________________
MAX9724A ACTIVE FILTER GAIN
vs. FREQUENCY
FREQUENCY (Hz)
GAIN (dB)
100k10k
-30
-25
-20
-15
-10
-5
0
5
10
-35
1k 1M
R
L
= 10kΩ
Figure 6. Frequency Response of Active Filter of Figure 4