Texas Instruments Boomer LM49360, User Manual

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Auxiliary Output Amplifier
The LM49360’s auxiliary output (AUXOUT) amplifier provides differential drive capability to loads that are connected across its
outputs. This results in output signals at the and AUX_OUT- pins that are 180 degrees out of phase with respect to
each other. This effectively doubles the maximum possible output swing for a specific supply voltage when compared to single-
ended output configurations. The differential output configuration also allows the load to be isolated from ground since both the
and AUX_OUT- pins are biased at the same DC potential. This eliminates the need for any large and expensive DC
blocking capacitors at the AUXOUT amplifier outputs. The load can then be directly connected to the positive and negative outputs
of the AUXOUT amplifier which then isolates it from any ground noise, thereby improving signal-to-noise-ratio (SNR) and power
supply rejection ratio (PSRR).
The AUXOUT amplifier has two modes of operation. The primary mode of operation is high current drive mode (Earpiece Mode)
where the AUXOUT amplifier can be used to differentially drive a mono earpiece speaker. The secondary mode of operation is
low current drive mode where the AUXOUT amplifier operates in a power saving mode (AUX_LINE_OUT Mode) to provide a
differential output that is used as a mono differential line level input to a standalone mono differential input class D amplifier
(LM4675) for stereo loudspeaker applications.
TABLE 43. OUTPUT_OPTIONS (0x14h)
Bits Field Description
0 RSVD Reserved
3:1 LR_HP_LEVEL This sets the gain of the left and right headphone amplifiers. The gain of the left and right headphone
amplifiers are always set to the same level.
LR_HP_LEVEL Gain (dB)
000 0
001 –1.5
010 –3
011 –6
100 –9
101 –12
110 –15
111 –18
4 AUX_NEG_6dB This sets the gain of the Auxiliary output amplifier.
AUX_NEG_6dB Gain (dB)
0 0
1 –6
5 AUX_LINE_OUT This sets the Auxiliary output amplifier mode of operation.
AUX_LINE_OUT Auxiliary Output Mode
0 Earpiece Amplifier
1 AUX_LINE_OUT
7:6 LS_LEVEL This sets the gain of the Class D loudspeaker amplifier.
LS_LEVEL Gain (dB)
00 0
01 4
10 8
11 12
TABLE 44. ADC_INPUT (0x15h)
Bits Field Description
0 DACR_ADCR The right DAC output is added to the ADC right input.
1 DACL_ADCL The left DAC output is added to the ADC left input.
2 MIC_ADCR The MIC input is added to the ADC right input.
3 MIC_ADCL The MIC input is added to the ADC left input.
4 AUX_ADCR The AUX input is added to the ADC right input.
5 MONO_ADCL The MONO input is added to the ADC left input.
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LM49360