參數(shù)資料
型號(hào)： MAX9877AERP+T
廠商： Maxim Integrated Products
文件頁(yè)數(shù)： 21/31頁(yè)
文件大?。?/td> 0K
描述： IC SUBSYSTEM MONO AUD 20MAXFILM
產(chǎn)品培訓(xùn)模塊： Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
標(biāo)準(zhǔn)包裝： 2,500
系列： DirectDrive®
類型： D 類
輸出類型： 1-通道（單聲道），帶立體聲耳機(jī)
在某負(fù)載時(shí)最大輸出功率 x 通道數(shù)量： 825mW x 1 @ 4 歐姆; 53mW x 2 @ 16 歐姆
電源電壓： 2.7 V ~ 5.25 V
特點(diǎn)： 消除爆音，I²C，輸入多路復(fù)用器，短路和熱保護(hù)，關(guān)機(jī)，音量控制
安裝類型： 表面貼裝
供應(yīng)商設(shè)備封裝： 20-UCSP
封裝/外殼： 20-WFBGA，CSPBGA
包裝： 帶卷 (TR)
Increasing the value of C1 reduces the charge-pump out-
put resistance to an extent. Above 1F, the on-resistance
of the switches and the ESR of C1 and C2 dominate.
Output Holding Capacitor (C2)
The output capacitor value and ESR directly affect the
ripple at VSS. Increasing the value of C2 reduces 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. Load Resistance graph
in the
Typical Operating Characteristics.
PVDD Bulk Capacitor (C3)
In addition to the recommended PVDD bypass capaci-
tance, bulk capacitance equal to C3 should be used.
Place the bulk capacitor as close to the device as possible.
Supply Bypassing,
Layout, and Grounding
Proper layout and grounding are essential for optimum
performance. Use wide traces for the power-supply
inputs and amplifier outputs to minimize losses due to
parasitic trace resistance. Wide 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 PCB. Route all
traces that carry switching transients away from GND
and the traces/components in the audio signal path.
Connect PVDD to a 2.7V to 5.25V source. Bypass PVDD
to the PGND pin with a 1F ceramic capacitor.
Additional bulk capacitance should be used to prevent
power-supply pumping. Place the bypass capacitors
as close to the MAX9877A as possible.
Connect VDD to PVDD. Bypass VDD to GND with a 1F
capacitor. Place the bypass capacitors as close to the
MAX9877A as possible.
RF Susceptibility
GSM radios transmit using time-division multiple
access (TDMA) with 217Hz intervals. The result is an
RF signal with strong amplitude modulation at 217Hz
that is easily demodulated by audio amplifiers. Figure
14 shows the susceptibility of the MAX9877A to a trans-
mitting GSM radio placed in close proximity. Although
there is measurable noise at 217Hz and its harmonics,
the noise is well below the threshold of hearing using
typical headphones.
In RF applications, improvements to both layout and
component selection decreases the MAX9877A’s sus-
ceptibility to RF noise and prevent RF signals from
being demodulated into audible noise. Trace lengths
should be kept below 1/4 the wavelength of the RF fre-
quency of interest. Minimizing the trace lengths pre-
vents them from functioning as antennas and coupling
RF signals into the MAX9877A. The wavelength
λ in
meters is given by:
λ = c/f
where c = 3 x 108 m/s, and f = the RF frequency of
interest.
Route audio signals on middle layers of the PCB to
allow ground planes above and below shield them from
RF interference. Ideally the top and bottom layers of the
PCB should primarily be ground planes to create effec-
tive shielding.
Additional RF immunity can also be obtained from rely-
ing on the self-resonant frequency of capacitors as it
exhibits the frequency response similar to a notch filter.
Depending on the manufacturer, 10pF to 20pF capaci-
tors typically exhibit self resonance at RF frequencies.
These capacitors, when placed at the input pins, can
effectively shunt the RF noise at the inputs of the
MAX9877A. For these capacitors to be effective, they
must have a low-impedance, low-inductance path to
the ground plane. Do not use microvias to connect to
the ground plane as these vias do not conduct well at
RF frequencies.
MAX9877AERP
Low RF Susceptibility, Mono Audio
Subsystem with DirectDrive Headphone Amplifier
28
______________________________________________________________________________________
RF SUSCEPTIBILITY
MAX9877A
fig14
FREQUENCY (Hz)
EFFICIENCY
(dB
)
10k
1k
100
-130
-110
-90
-70
-50
-30
-10
-150
10
100k
THRESHOLD OF HEARING
MAX9877A
NOISE FLOOR
Figure 14. MAX9877A Susceptibility to a GSM Cell Phone
Radio
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