max9702etit Maxim Integrated Products, Inc., max9702etit Datasheet - Page 26

• Manufacturer Part Number: max9702etit
• Description: Max9702 1.8w, Filterless, Stereo, Class D Audio Power Amplifier And Directdrive Stereo Headphone Amplifier
• Manufacturer: Maxim Integrated Products, Inc.

BIAS is the output of the internally generated DC bias
voltage. The BIAS bypass capacitor, C
PSRR and THD+N by reducing power supply and other
noise sources at the common-mode bias node, and
also generates the clickless/popless, startup/shutdown
DC bias waveforms for the speaker amplifiers. Bypass
BIAS with a 1µF capacitor to GND.
Use capacitors with an ESR less than 100mΩ for opti-
mum performance. Low-ESR ceramic capacitors mini-
mize the output resistance of the charge pump. Most
surface-mount ceramic capacitors satisfy the ESR
requirement. For best performance over the extended
temperature range, select capacitors with an X7R
dielectric. Table 8 lists suggested manufacturers.
The value of the flying capacitor (C1) affects the output
resistance of the charge pump. A C1 value that is too
small degrades the device’s ability to provide sufficient
current drive, which leads to a loss of output voltage.
Increasing the value of C1 reduces the charge-pump out-
put resistance to an extent. Above 1µF, the on-resistance
of the switches and the ESR of C1 and C2 dominate.
The output capacitor value and ESR directly affect the
ripple at CPV
output ripple. Likewise, decreasing the ESR of C2
reduces both ripple and output resistance. Lower
capacitance values can be used in systems with low
maximum output power levels. See the Output Power
vs. Charge-Pump Capacitance and Load Resistance
graph in the Typical Operating Characteristics.
The CPV
impedance of the power supply and reduces the
impact of the MAX9702’s charge-pump switching tran-
1.8W, Filterless, Stereo, Class D Audio Power
Amplifier and DirectDrive Stereo Headphone Amplifier
Table 8. Suggested Capacitor Manufacturers
26
Taiyo Yuden
TDK
______________________________________________________________________________________
DD
SUPPLIER
bypass capacitor (C3) lowers the output
SS
. Increasing the value of C2 reduces
Charge-Pump Capacitor Selection
CPV
Output Capacitor (C2)
Flying Capacitor (C1)
DD
Bypass Capacitor
800-348-2496
807-803-6100
BIAS Capacitor
PHONE
BIAS
, improves
sients. Bypass CPV
physically close to the CPV
for C3 that is equal to C1.
Proper layout and grounding are essential for optimum
performance. Use large traces for the power-supply
inputs and amplifier outputs to minimize losses due to
parasitic trace resistance. Large traces also aid in mov-
ing heat away from the package. Proper grounding
improves audio performance, minimizes crosstalk
between channels, and prevents any switching noise
from coupling into the audio signal. Connect PGND and
GND together at a single point on the PC board. Route
all traces that carry switching transients away from GND
and the traces/components in the audio signal path.
Connect all of the power-supply inputs (CPV
and PV
tor to PGND and CPV
Bypass V
bypass capacitors as close to the MAX9702 as possi-
ble. Place a bulk capacitor between PV
if needed.
Use large, low-resistance output traces. Current drawn
from the outputs increases as load impedance
decreases. High-output trace resistance decreases the
power delivered to the load. Large output, supply, and
GND traces decrease the thermal impedance of the
system, allowing more heat to move from the MAX9702
to the air.
The MAX9702 thin QFN-EP package features an
exposed thermal pad on its underside. This pad lowers
the package’s thermal impedance by providing a
direct-heat conduction path from the die to the printed
circuit board. The exposed pad is internally connected
to V
plane if possible or to V
847-925-0899
847-390-4405
SS
. Connect the exposed pad to an isolated
FAX
DD
) together. Bypass PV
DD
with 1µF capacitor to GND. Place the
DD
Supply Bypassing, Layout,
DD
with C3 to PGND and place it
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with a 1µF capacitor to PGND.
SS
DD
.
and PGND. Use a value
DD
with a 0.1µF capaci-
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and Grounding
DD
and PGND,
DD
, V
DD
,