MAX9765ETJ MAXIM [Maxim Integrated Products], MAX9765ETJ Datasheet - Page 25

• Manufacturer Part Number: MAX9765ETJ
• Description: 750mW Audio Amplifiers with Headphone Amp, Microphone Preamp, and Input Mux
• Manufacturer: MAXIM [Maxim Integrated Products]

The MAX9765/MAX9766/MAX9767 require output-cou-
pling capacitors to operate in single-ended (head-
phone) mode. The output-coupling capacitor blocks the
DC component of the amplifier output, preventing DC
current from flowing to the load. The output capacitor
and the load impedance form a highpass filter with a
-3dB point determined by:
As with the input capacitor, choose C
f
Setting f
quency response.
Load impedance is a concern when choosing C
Load impedance can vary, changing the -3dB point of
the output filter. A lower impedance increases the cor-
ner frequency, degrading low-frequency response.
Select C
bination yields an adequate response. Select capaci-
tors with low ESR.
BIAS is the output of the internally generated 1.5VDC
bias voltage. The BIAS bypass capacitor, C
improves PSRR and THD+N by reducing power supply
and other noise sources at the common-mode bias
node, and also generates the clickless/popless, start-
up/shutdown DC bias waveforms for the speaker ampli-
fiers. Bypass BIAS with a 1µF capacitor to GND.
-3dB
is well below the lowest frequency of interest.
OUT
-3dB
750mW Audio Amplifiers with Headphone Amp,
such that the worst-case load/C
too high affects the amplifier‘s low-fre-
f
−
______________________________________________________________________________________
3
dB
=
2π
Output-Coupling Capacitor
R C
L OUT
1
Microphone Preamp, and Input Mux
BIAS Capacitor
OUT
such that
OUT
BIAS
com-
OUT
.
,
Smaller capacitor values produce faster turn-on/off
times and may impact the click/pop levels.
Proper power-supply bypassing ensures low-noise,
low-distortion performance. Place a 0.1µF ceramic
capacitor from V
capacitance as required by the application. Bypass
PV
capacitors as close to the device as possible.
Good PC board layout is essential for optimizing perfor-
mance. Use large traces for the power-supply inputs
and amplifier outputs to minimize losses due to para-
sitic trace resistance, as well as route heat away from
the device. Good grounding improves audio perfor-
mance, minimizes crosstalk between channels, and
prevents any digital switching noise from coupling into
the audio signal. If digital signal lines must cross over
or under audio signal lines, ensure that they cross per-
pendicular to each other.
The MAX9765/MAX9766/MAX9767 thin QFN packages
feature exposed thermal pads on their undersides. This
pad lowers the package’s thermal resistance by provid-
ing a direct heat conduction path from the die to the
printed circuit board. Connect the pad to signal ground
by using a large pad, or multiple vias to the ground
plane.
DD
with a 100µF capacitor to GND. Locate bypass
DD
to GND. Add additional bulk
Layout and Grounding
Supply Bypassing
25