max97002 Maxim Integrated Products, Inc., max97002 Datasheet - Page 33

• Manufacturer Part Number: max97002
• Description: Audio Subsystem With Mono Class D Speaker And Class H Headphone Amplifiers
• Manufacturer: Maxim Integrated Products, Inc.

Figure 12. Reading One Byte of Data from the MAX97002
Figure 13. Reading n-Bytes of Data from the MAX97002
Traditional Class D amplifiers require an output filter to
recover the audio signal from the amplifier’s output. The
filters add cost, increase the solution size of the amplifier,
and can decrease efficiency and THD+N performance.
The traditional PWM scheme uses large differential out-
put swings (2 x V
rents. Any parasitic resistance in the filter components
results in a loss of power, lowering the efficiency.
The MAX97002 does not require an output filter. The
device relies on the inherent inductance of the speaker
coil and the natural filtering of both the speaker and
the human ear to recover the audio component of the
square-wave output. Eliminating the output filter results
in a smaller, less costly, more efficient solution.
Because the frequency of the MAX97002 output is well
beyond the bandwidth of most speakers, voice coil
movement due to the square-wave frequency is very
small. Although this movement is small, a speaker not
designed to handle the additional power can be dam-
aged. For optimum results, use a speaker with a series
inductance > 10FH. Typical 8I speakers exhibit series
inductances in the 20FH to 100FH range.
S
ACKNOWLEDGE FROM MAX97002
S
ACKNOWLEDGE FROM MAX97002
Speaker and Class H Headphone Amplifiers
SLAVE ADDRESS
SLAVE ADDRESS
Applications Information
DD(P-P)
Filterless Class D Operation
R/W
R/W
0
) and causes large ripple cur-
Audio Subsystem with Mono Class D
0
ACKNOWLEDGE FROM MAX97002
ACKNOWLEDGE FROM MAX97002
REGISTER ADDRESS
REGISTER ADDRESS
REPEATED START
REPEATED START
A
Sr
ACKNOWLEDGE FROM MAX97002
A
Sr
ACKNOWLEDGE FROM MAX97002
SLAVE ADDRESS
GSM radios transmit using time-division multiple access
(TDMA) with 217Hz intervals. The result is an RF signal
with strong amplitude modulation at 217Hz and its har-
monics that are easily demodulated by audio amplifiers.
The MAX97002 is designed specifically to reject RF
signals; however, PCB layout has a large impact on the
susceptibility of the end product.
In RF applications, improvements to both layout and
component selection decreases the MAX97002’s sus-
ceptibility to RF noise and prevent RF signals from being
demodulated into audible noise. Trace lengths should
be kept below 1/4 of the wavelength of the RF frequency
of interest. Minimizing the trace lengths prevents them
from functioning as antennas and coupling RF signals
into the MAX97002. The wavelength (l) in meters is
given by:
where c = 3 x 10
interest.
Route the audio signals on the middle layers of the PCB
to allow the ground planes above and below to shield
them from RF interference. Ideally, the top and bottom
layers of the PCB should primarily be ground planes to
create effective shielding.
SLAVE ADDRESS
R/W
R/W
1
A
1
8
NOT ACKNOWLEDGE FROM MASTER
m/s, and f = the RF frequency of
A
l = c/f
DATA BYTE
1 BYTE
REGISTER ADDRESS POINTER
DATA BYTE
AUTOINCREMENT INTERNAL
1 BYTE
RF Susceptibility
REGISTER ADDRESS POINTER
AUTOINCREMENT INTERNAL
A
A
P
P
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