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参数资料
| 型号： | LM4753T |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 音频／视频放大 |
| 英文描述： | 11.8 W, 2 CHANNEL, AUDIO AMPLIFIER, PZFM15 |
| 封装： | TO-220, 15 PIN |
| 文件页数： | 15/16页 |
| 文件大小： | 511K |
| 代理商： | LM4753T |
Application Information (Continued)
If the sequence described above and shown in
Figure 4 is
not used, then the external circuitry shown in Figure 5 should
be used to minimize turn-on/off pops and protect the output
stage against SOA violations.
In
Figure 5 there are only a few components that are differ-
ent than the ones described earlier for lowpass filtering the
pin voltages. The new components are Q1, R2, R3, D1 and
D2. All of the other components will perform the same func-
tions that were previously described.
The explanation of how the circuit in
Figure 5 works will be
related to the timing waveforms in
Figure 6. The circuit in
Figure 5 protects the LM4753 from SOA violations by ensur-
ing that the enabling of the standby function when music is
playing will not quickly bring the biasing to ground before the
input signal is smoothly attenuated through the volume func-
tion. Again, this is important because any quick changes in
output current when driving an inductive load will cause a fly-
back voltage that may damage the IC.
As shown in
Figure 6, first notice that music is playing at the
output. When the mechanical standby switch is toggled from
ground (play mode) to 5V (standby mode), transistor Q1 is
quickly turned on, discharging capacitor C7, bringing the
voltage at the volume pin, pin 3, to ground. This quickly at-
tenuates the audio signal at the output as shown in
Figure 6.
While the input signal is being attenuated, the diode D1 be-
comes reverse biased and the voltage at the standby pin
starts to charge through R4, C8 and C9. There is also a finite
amount of current flowing through R5 as well, but because of
its high resistance, we can neglect it in the charge-up timing
of pin 9. Note that when the standby switch was grounded,
the diode D1 was clamping the standby pin low, setting the
initial voltage condition of C8 at a low voltage. Once C8
starts charging up, diode D2 becomes forward biased and
C9 also starts charging up. This brings the standby and mute
pin voltages up simultaneously. By the time the standby pin
voltage enables the standby function, the voltage at the vol-
ume pin will already have been ramped down to 0V and the
output signal will be close to 0V.
When the IC is in standby mode the biasing of the IC is
brought down to ground and the quiescent supply current is
around 7 mA. When the standby switch in
Figure 5 is toggled
DS100043-28
FIGURE 4. Turn-On/Off Sequence
www.national.com
8
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相关代理商/技术参数 |
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| LM4755 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Stereo 11W Audio Power Amplifier with Mute |
| LM4755_02 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Stereo 11W Audio Power Amplifier with Mute |
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| LM4755T/NOPB | 功能描述:IC AMP AUDIO PWR 11W AB TO220-9 RoHS:是 类别:集成电路 (IC) >> 线性 - 音頻放大器 系列:- 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:H 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:35mW x 2 @ 16 欧姆 电源电压:1.62 V ~ 1.98 V 特点:I²C，麦克风，静音，短路保护，音量控制 安装类型:表面贴装 供应商设备封装:25-WLP（2.09x2.09） 封装/外壳:25-WFBGA，WLCSP 包装:带卷 (TR) |
| LM4755T/NOPB | 制造商:Texas Instruments 功能描述:Audio Power Amplifier IC |
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