參數(shù)資料
型號(hào)： MAX9702B
廠商： Maxim Integrated Products, Inc.
英文描述： 1.8W, Filterless, Stereo, Class D Audio Power Amplifier and DirectDrive Stereo Headphone Amplifier
中文描述： 1.8W的，濾波，立體聲D類音頻功率放大器和DirectDrive立體聲耳機(jī)放大器
文件頁(yè)數(shù)： 24/32頁(yè)
文件大?。?/td> 1411K
代理商： MAX9702B
M
Shutdown
The MAX9702 features a 0.1μA shutdown mode that
reduces power consumption to extend battery life.
Shutdown is controlled by the hardware or software
interface. Drive
SHDN
low to disable the drive ampli-
fiers, bias circuitry, charge pump, and set the head-
phone amplifier output impedance to 1k
. Similarly, the
MAX9702 enters shutdown when bit 7 (B7) in the con-
trol register is set to zero. Connect
SHDN
to V
DD
and
set bit 7 = 1 for normal operation (see Table 7). The I
2
C
interface is active and the contents of the command
register are not affected when in shutdown. This allows
the master to write to the MAX9702 while in shutdown.
Table 7. Shutdown Control
(SHDN
)
Applications Information
Filterless Class D Operation
Traditional Class D amplifiers require an output filter to
recover the audio signal from the amplifier’s PWM out-
put. The filters add cost, increase the solution size of
the amplifier, and can decrease efficiency. The tradi-
tional PWM scheme uses large differential output
swings 2 x V
DD(P-P)
and causes large ripple currents.
Any parasitic resistance in the filter components results
in a loss of power, lowering the efficiency.
The MAX9702 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. By eliminating the output filter, this
results in a smaller, less costly, more efficient solution.
Because the frequency of the MAX9702 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 may be dam-
aged. For optimum results, use a speaker with a series
inductance >10μH. Typical 8
speakers, for portable
audio applications, exhibit series inductances in the
range of 20μH to 100μH.
Class D Output Offset
Unlike a Class AB amplifier, the output offset voltage of
Class D amplifiers does not noticeably increase quies-
cent current draw when a load is applied. This is due to
the power conversion of the Class D amplifier. For
example, an 8mV DC offset across an 8
load results
in 1mA extra current consumption in a Class AB
device. In the Class D case, an 8mV offset into 8
equates to an additional power drain of 8μW. Due to
the high efficiency of the Class D amplifier, this repre-
sents an additional quiescent current draw of
8μW/(V
DD
/100 x
η
), which is on the order of a few
microamps.
DC-Coupled Input
The input amplifier can accept DC-coupled inputs that
are biased to the amplifier’s bias voltage. DC-coupling
eliminates the input-coupling capacitors, reducing
component count to potentially one external component
(see the
System Diagram
). However, the highpass fil-
tering effect of the capacitors is lost, allowing low-fre-
quency signals to feed through to the load.
Power Supplies
The MAX9702 has different supplies for each portion of
the device, allowing for the optimum combination of
headroom power dissipation and noise immunity. The
speaker amplifiers are powered from PV
DD
. PV
DD
can
range from 2.5V to 5.5V and must be connected to the
same potential as V
DD
. The headphone amplifiers are
powered from V
DD
and V
SS
. V
DD
is the positive supply
of the headphone amplifiers and can range from 2.5V
to 5.5V. V
SS
is the negative supply of the headphone
amplifiers. Connect V
SS
to CPV
SS
. The charge pump is
powered by CPV
DD
. Connect CPV
DD
to V
DD
for normal
operation. The charge pump inverts the voltage at
CPV
DD
, and the resulting voltage appears at CPV
SS
.
The remainder of the device is powered by V
DD
.
Component Selection
Input Filter
An input capacitor, C
IN
, in conjunction with the input
impedance of the MAX9702 forms a highpass filter that
removes the DC bias from an incoming signal. The AC-
coupling capacitor allows the amplifier to automatically
bias the signal to an optimum DC level. Assuming zero-
source impedance, the -3dB point of the highpass filter
is given by:
Choose C
IN
such that f
-3dB
is well below the lowest fre-
quency of interest. Use capacitors whose dielectrics
have low-voltage coefficients, such as tantalum or alu-
minum electrolytic. Capacitors with high-voltage coeffi-
cients, such as ceramics, may result in increased
distortion at low frequencies.
f
R C
π
dB
3
=
1
2
1.8W, Filterless, Stereo, Class D Audio Power
Amplifier and DirectDrive Stereo Headphone Amplifier
24
______________________________________________________________________________________
B7
0
1
FUNCTION
Soft shutdown
Normal operation
相關(guān)PDF資料
PDF描述
MAX9703 Hex 2-Input OR Drivers 20-CDIP -55 to 125
MAX9703-MAX9704 15W, Filterless, Spread-Spectrum Mono/Stereo Class D Amplifiers
MAX9703ETJ 15W, Filterless, Spread-Spectrum Mono/Stereo Class D Amplifiers
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MAX9702BETI+ 制造商:Maxim Integrated Products 功能描述:AUD AMP HDPH/SPKR 2CH STEREO 1.8W/0.045W CLS-AB/CLS-D 28TQFN - Rail/Tube
MAX9702BETI+T 制造商:Maxim Integrated Products 功能描述:AUD AMP HDPH/SPKR 2CH STEREO 1.8W/0.045W CLS-AB/CLS-D 28TQFN - Tape and Reel
MAX9702BEUI+ 制造商:Maxim Integrated Products 功能描述:AUD AMP HDPH/SPKR 2CH STEREO 1.8W/0.045W CLS-AB/CLS-D 28TSSO - Rail/Tube
MAX9702BEUI+T 制造商:Maxim Integrated Products 功能描述:AUD AMP HDPH/SPKR 2CH STEREO 1.8W/0.045W CLS-AB/CLS-D 28TSSO - Tape and Reel
MAX9702ETI+ 功能描述:音頻放大器 1.8W Filterless Class D Audio Amp RoHS:否 制造商:STMicroelectronics 產(chǎn)品:General Purpose Audio Amplifiers 輸出類型:Digital 輸出功率: THD + 噪聲: 工作電源電壓:3.3 V 電源電流: 最大功率耗散: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TQFP-64 封裝:Reel
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