LM49352RLX/NOPB National Semiconductor, LM49352RLX/NOPB Datasheet - Page 69

• Manufacturer Part Number: LM49352RLX/NOPB
• Description: IC AMP AUDIO MONO D1.4W 36USMD
• Manufacturer: National Semiconductor
• Series: Boomer®, PowerWise®r
• Type: Class Dr

Specifications of LM49352RLX/NOPB

• Output Type: 1-Channel (Mono) with Mono and Stereo Headphones
• Max Output Power X Channels @ Load: 1.4W x 1 @ 8 Ohm; 65mW x 2 @ 32 Ohm
• Features: Depop, Differential Inputs, I²C, I²S, Microphone, Shutdown, Volume Control
• Mounting Type: Surface Mount
• Package / Case: 36-MicroSMDxt
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Supply: -
• Other names: LM49352RLX

Limiter
The LM49352’s ALC features a limiter function. The purpose of the limiter is to limit the maximum level of the audio signal to the
specified ALC target level. When the limiter is enabled, the ALC will decrease the gain of the volume control whenever the audio
signal is higher than the specified target level. The programmed I
C gain setting when the limiter is first enabled is the maximum
2
gain setting that the ALC limiter will apply to the audio signal. Gain increases beyond the original I
2
C gain setting are disabled.
This is in contrast to ALC operation with the limiter disabled, where the ALC may increase gain of audio signals below target level
using gain settings beyond the original I
2
C gain setting. Therefore, it is important to set the gain of the audio path to the desired
setting before enabling the ALC limiter function.
The limiter’s target level can be set just below the clipping level of the output amplifier or ADC in order to prevent harsh distortions
delivered to the loudspeaker or headphone on the receiving end. This method of ALC limiter operation is also known as “no clip”
mode. Operating the ALC limiter in “no clip” mode maximizes the dynamic range of the audio amplifier or ADC while ensuring that
the audio signal will never clip. Utilizing the ALC limiter in “no clip” mode also protects the loudspeaker from damage due to harmful
overdriven conditions.
The ALC limiter’s target level can also be set for a predetermined maximum output power or voltage level. This method of ALC
limiter operation is known as “power limit” mode. Operating the ALC limiter in “power limit” mode prevents the speaker or headphone
from playing at unsafe hearing levels that can permanently damage the end user’s ears. “Power limit” operation is especially useful
for applications such as listening to music through a set of headphones. Another benefit of using the ALC limit in “power limit” mode
is to extend battery life by reducing power consumption of the output amplifiers during audio playback.
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FIGURE 24. ALC Limiter
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