参数资料
型号: LM4839MT/NOPB
厂商: NATIONAL SEMICONDUCTOR CORP
元件分类: 音频控制
英文描述: 2 CHANNEL(S), TONE CONTROL CIRCUIT, PDSO28
封装: TSSOP-28
文件页数: 10/34页
文件大小: 1104K
代理商: LM4839MT/NOPB
Application Information (Continued)
When the bass boost is enabled, the output amplifiers will be
internally set at a gain of 2 at low frequencies (gain of 4 in
bridged mode). As shown in Figure 1, CBS sets the cutoff
frequency for the bass boost. At low frequencies, the capaci-
tor will be virtually an open circuit. At high frequencies, the
capacitor will be virtually a short circuit. As a result of this, the
gain of the bridge amplifier is increased as low frequencies.
A first order pole is formed with a corner frequency at:
f
c = 1/(2π10kCBS)
(9)
With CBS = 0.1uF, a first order pole is formed with a corner
frequency of 160Hz.
DC VOLUME CONTROL
The LM4839 has an internal stereo volume control whose
setting is a function of the DC voltage applied to the DC VOL
CONTROL pin.
The LM4839 volume control consists of 31 steps that are
individually selected by a variable DC voltage level on the
volume control pin. The range of the steps, controlled by the
DC voltage, are from 0dB - 78dB. Each gain step corre-
sponds to a specific input voltage range, as shown in table 2.
To minimize the effect of noise on the volume control pin,
which can affect the selected gain level, hysteresis has been
implemented. The amount of hysteresis corresponds to half
of the step width, as shown in Volume Control Characteriza-
tion Graph (DS200133-40).
For highest accuracy, the voltage shown in the ’recom-
mended voltage’ column of the table is used to select a
desired gain. This recommended voltage is exactly halfway
between the two nearest transitions to the next highest or
next lowest gain levels.
The gain levels are 1dB/step from 0dB to -6dB, 2dB/step
from -6dB to -36dB, 3dB/step from -36dB to -47dB, 4dB/step
from -47db to -51dB, 5dB/step from -51dB to -66dB, and
12dB to the last step at -78dB.
LM4839
www.national.com
18
相关PDF资料
PDF描述
LM4839MTX/NOPB 2 CHANNEL(S), TONE CONTROL CIRCUIT, PDSO28
LM4839LQ/NOPB 2 CHANNEL(S), TONE CONTROL CIRCUIT, CQCC28
LM4839LQX/NOPB 2 CHANNEL(S), TONE CONTROL CIRCUIT, CQCC28
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LM4840LQ/NOPB 2 CHANNEL(S), VOLUME CONTROL CIRCUIT, QCC28
相关代理商/技术参数
参数描述
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