max9702etit Maxim Integrated Products, Inc., max9702etit Datasheet - Page 25

• 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.

Amplifier and DirectDrive Stereo Headphone Amplifier
Other considerations when designing the input filter
include the constraints of the overall system and the
actual frequency band of interest. Although high-fidelity
audio calls for a flat-gain response between 20Hz and
20kHz, portable voice-reproduction devices such as
cellular phones and two-way radios need only concen-
trate on the frequency range of the spoken human voice
(typically 300Hz to 3.5kHz). In addition, speakers used
in portable devices typically have a poor response
below 300Hz. Taking these two factors into considera-
tion, the input filter may not need to be designed for a
20Hz to 20kHz response, saving both board space and
cost due to the use of smaller capacitors.
Figure 13. Optional Speaker Amplifier Output Filter
<75mm OF SPEAKER CABLE.
MAX9702
TYPICAL APPLICATION
OUTR+
OUTL+
OUTL-
OUTR-
(a)
______________________________________________________________________________________
1.8W, Filterless, Stereo, Class D Audio Power
MAX9702
APPLICATIONS USING CABLE LENGTHS
OUTR+
OUTL+
OUTR-
OUTL-
COMMON-MODE CHOKE FOR
GREATER THAN 75mm.
AT 100MHz
AT 100MHz
800Ω
800Ω
(b)
100pF
100pF
100pF
100pF
The MAX9702 does not require an output filter. The
device passes FCC emissions standards with 75mm of
unshielded speaker cables. However, output filtering
can be used if a design is failing radiated emissions
due to board layout or cable length, or the circuit is
near EMI-sensitive devices. Use a ferrite bead filter
when radiated frequencies above 10MHz are of con-
cern. Use an LC filter when radiated frequencies below
10MHz are of concern, or when long leads (>200mm)
connect the amplifier to the speaker. Figure 13 shows
optional speaker amplifier output filters.
MAX9702
OUTR+
OUTL+
OUTR-
OUTL-
SENSITIVE TO EMI BELOW 10MHz.
LENGTHS LONGER THAN 200mm
LC FILTER WHEN USING CABLE
IN APPLICATIONS THAT ARE
15µH
15µH
15µH
15µH
0.033µF
0.033µF
0.033µF
0.033µF
(c)
0.15µF
0.15µF
Output Filter
22Ω
22Ω
22Ω
22Ω
0.068µF
0.068µF
0.068µF
0.068µF
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