参数资料
型号: MAX9789BETJ+T
厂商: Maxim Integrated Products
文件页数: 8/28页
文件大小: 0K
描述: IC AMP AUDIO 2W STER AB 32TQFN
产品培训模块: Lead (SnPb) Finish for COTS
Obsolescence Mitigation Program
标准包装: 2,500
系列: DirectDrive®
类型: AB 类
输出类型: 2-通道(立体声)带立体声耳机
在某负载时最大输出功率 x 通道数量: 2W x 2 @ 4 欧姆; 100mW x 2 @ 16 欧姆
电源电压: 4.5 V ~ 5.5 V
特点: 消除爆音,静音,短路保护和热保护,关机
安装类型: 表面贴装
供应商设备封装: 32-TQFN-EP(5x5)
封装/外壳: 32-WFQFN 裸露焊盘
包装: 带卷 (TR)
MAX9789/MAX9790
Windows Vista-Compliant, Stereo Class AB Speaker
Amplifiers and DirectDrive Headphone Amplifiers
16
______________________________________________________________________________________
The voltage coefficient of the capacitor, the change
in capacitance due to a change in the voltage
across the capacitor, distorts the audio signal. At
frequencies around the -3dB point, this effect is
maximized and the voltage coefficient appears as
frequency-dependent distortion. Figure 3 shows the
THD+N introduced by two different capacitor
dielectrics. Note that around the -3dB point, THD+N
increases dramatically.
The combination of low-frequency attenuation and fre-
quency-dependent distortion compromises audio
reproduction. DirectDrive improves low-frequency
reproduction in portable audio equipment that empha-
sizes low-frequency effects, such as multimedia lap-
tops, MP3, CD, and DVD players (See Table 2).
Charge Pump
The MAX9789/MAX9790 feature a low-noise charge
pump. The 550kHz switching frequency is well beyond
the audio range, and does not interfere with the audio
signals. The switch drivers feature a controlled switching
speed that minimizes noise generated by switching
transients. Limiting the switching speed of the charge
pump minimizes the di/dt noise caused by the parasitic
bond wire and trace inductance.
BIAS
The MAX9789/MAX9790 feature an internally generat-
ed, power-supply independent, common-mode bias
voltage of 1.8V referenced to GND. BIAS provides both
click-and-pop suppression and sets the DC bias level
for the amplifiers. The BIAS pin should be bypassed to
GND with a 1F capacitor. No external load should be
applied to BIAS. Any load lowers the BIAS voltage,
affecting the overall performance of the device.
Headphone and Speaker Amplifier Gain
The MAX9789/MAX9790 feature programmable speak-
er amplifier gain, set by the logic voltages applied to
pins GAIN1 and GAIN2. Table 3 shows the logic com-
binations that can be applied to pins GAIN1 and GAIN2
and their affects on the speaker amplifier gain. The
headphone amplifier gain is fixed at 3.5dB.
0
-30
1
10
100
1k
10k
100k
LOW-FREQUENCY ROLLOFF
(RL = 16
Ω)
-24
-27
-12
-15
-18
-21
-6
-9
-3
FREQUENCY (Hz)
ATTENUATION
(dB)
DirectDrive
330
μF
220
μF
100
μF
33
μF
Figure 2. Low-Frequency Attenuation of Common DC-Blocking
Capacitor Values
ADDITIONAL THD+N DUE TO
DC-BLOCKING CAPACITORS
FREQUENCY (Hz)
THD+N
(%)
10k
1k
100
0.001
0.01
0.1
1
10
0.0001
10
100k
TANTALUM
COUT = 100
μF
RL = 16
Ω
ALUM/ELEC
Figure 3. Distortion Contributed by DC-Blocking Capacitors
MAX9789/MAX9790
GAIN1
GAIN2
SPEAKER MODE
GAIN (dB)
HEADPHONE
MODE GAIN (dB)
0
6
3.5
0
1
10
3.5
1
0
15.6
3.5
1
21.6
3.5
Table 3. MAX9789/MAX9790
Programmable Gain Settings
f-3dB (Hz)
COUT (F)
RL = 16
Ω
RL = 32
Ω
22
452
226
33
301
151
100
99
50
220
45
23
330*
30
15
470
21
11
Table 2. Low-Frequency Rolloff
*Vista requirement for 32Ω load.
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