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| 型号： | MAX9725DETC+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 17/17页 |
| 文件大小： | 0K |
| 描述： | IC AMP AUDIO .025W STER 12TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 75 |
| 系列： | DirectDrive® |
| 类型： | AB 类 |
| 输出类型： | 耳机，2-通道（立体声） |
| 在某负载时最大输出功率 x 通道数量： | 25mW x 2 @ 16 欧姆 |
| 电源电压： | 900 mV ~ 1.8 V |
| 特点： | 消除爆音，短路保护，关机 |
| 安装类型： | 表面贴装 |
| 供应商设备封装： | 12-TQFN-EP（4x4） |
| 封装/外壳： | 12-WQFN 裸露焊盘 |
| 包装： | 管件 |
MAX9725
Low-Frequency Response
Large DC-blocking capacitors limit the amplifier’s low-
frequency response and can distort the audio signal:
1) The impedance of the headphone load and the DC-
blocking capacitor forms a highpass filter with the
-3dB point set by:
where RL is the impedance of the headphone and
COUT is the value of the DC-blocking capacitor. The
highpass filter is required by conventional single-
ended, single power-supply headphone drivers to
block the midrail DC-bias component of the audio
signal from the headphones. The drawback to the
filter is that it can attenuate low-frequency signals.
Larger values of COUT reduce this effect but result
in physically larger, more expensive capacitors.
Figure 2 shows the relationship between the size of
COUT and the resulting low-frequency attenuation.
Note that the -3dB point for a 16
Ω headphone with
a 100F blocking capacitor is 100Hz, well within the
normal audio band, resulting in low-frequency
attenuation of the reproduced signal.
2) The voltage coefficient of the DC-blocking capacitor
contributes distortion to the reproduced audio signal
as the capacitance value varies when the function of
the voltage across the capacitor changes. At low
frequencies, the reactance of the capacitor domi-
nates at frequencies below the -3dB point and the
voltage coefficient appears as frequency-dependent
distortion. Figure 3 shows the THD+N introduced by
two different capacitor dielectric types. Note that
below 100Hz, THD+N increases rapidly.
The combination of low-frequency attenuation and fre-
quency-dependent distortion compromises audio
reproduction in portable audio equipment that empha-
sizes low-frequency effects such as multimedia lap-
tops, as well as MP3, CD, and DVD players. These
low-frequency, capacitor-related deficiencies are elimi-
nated by using DirectDrive technology.
Charge Pump
The MAX9725 features a low-noise charge pump. The
580kHz 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 turn-on and turn-off
transients. The di/dt noise caused by the parasitic bond
wire and trace inductance is minimized by limiting the
turn-on/off speed of the charge pump. Additional high-
frequency noise attenuation can be achieved by
increasing the size of C2 (see the
Functional Diagrams).
Extra noise attenuation is not typically required.
Shutdown
The MAX9725’s low-power shutdown mode reduces
supply current to 0.6A. Driving
SHDN low disables the
amplifiers and charge pump. The driver’s output imped-
ance
is
typically
50k
Ω (MAX9725A), 37.5kΩ
(MAX9725B), 25k
Ω (MAX9725C), 100kΩ (MAX9725D),
or RF (MAX9725E) when in shutdown mode.
f
2R C
-3dB
L OUT
=
1
π
Figure 2. Low-Frequency Attenuation for Common DC-Blocking
Capacitor Values
LF ROLLOFF (16
Ω LOAD)
FREQUENCY (Hz)
ATTENUATION
(dB)
100
-30
-25
-20
-10
-3dB CORNER FOR
100
μF IS 100Hz
-15
-5
-3
0
-35
10
1k
33
μF
330
μF
220
μF
100
μF
Figure 3. Distortion Contributed By DC-Blocking Capacitors
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
ALUM/ELEC
1V, Low-Power, DirectDrive, Stereo Headphone
Amplifier with Shutdown
_______________________________________________________________________________________
9
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX9725DETC+ | 功能描述:音频放大器 1V DirectDrive Headphone Amplifier RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel |
| MAX9725DETC+T | 功能描述:音频放大器 1V DirectDrive Headphone Amplifier RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel |
| MAX9725DETC-T | 功能描述:音频放大器 RoHS:否 制造商:STMicroelectronics 产品:General Purpose Audio Amplifiers 输出类型:Digital 输出功率: THD + 噪声: 工作电源电压:3.3 V 电源电流: 最大功率耗散: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:TQFP-64 封装:Reel |
| MAX9725EC/W WAF | 制造商:Maxim Integrated Products 功能描述: |
| MAX9725EEBC+ | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
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