lm4832 National Semiconductor Corporation, lm4832 Datasheet - Page 17

• Manufacturer Part Number: lm4832
• Description: Digitally Controlled Tone And Volume Circuit With Stereo Audio Power Amplifier, Microphone Preamp Stage And National 3d Sound
• Manufacturer: National Semiconductor Corporation

Application Information
GENERAL PURPOSE OUTPUT PIN
The General Purpose Output pin is intended to be used as a
control signal for other devices, such as an external power
amplifier. This pin is controlled through the I
is not relatedto any other functions within the LM4832. Refer
to the Truth Tables section for the proper I
utilize this function.
Figure 7 shows an example of using the General Purpose
Output to interface with an external power amp. In this case,
the external power amp is the LM4755 stereo 10 watt per
LOOP IN/OUT PINS
The Loop In and Loop Out pins are used when an application
requires a special function to be performed on the audio
signal. As shown in Figure 7, the audio signal is taken from
the Loop Out pin and sent to an external signal processor.
After the signal is processed externally, it is fed back into the
Loop In pin.
An example of where this functionality would be used is
computer speakers. The external loop could be used to
provide bass boost to counteract the speaker’s natural or
baffle-induced rolloff.
10W/ch System with I
(Continued)
2
C interface and
2
C data bits to
FIGURE 6. Tone Control Diagram
2
C Controlled Tone,Volume and 3D Sound
FIGURE 7.
17
channel (rms) power amplifier with mute. AC-coupling ca-
pacitors must be used to remove the DC bias present be-
tween the LM4832 outputs and the external power amplifier
inputs.
Prior to placing any of the preamp circuitry in shutdown, the
General Purpose Output should be used to disable the ex-
ternal power amplifier.This will prevent any shutdown tran-
sients in the preamp circuitry from being amplified by the
external power amplifier.
Since the Loop In pin goes directly to the input of a CMOS
amplifier, the input impedance is very high. The Loop Out pin
is driven by the input attenuation amplifier, which is capable
of driving impedances as low as 1 kΩ.
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