lm49370rl National Semiconductor Corporation, lm49370rl Datasheet - Page 33

• Manufacturer Part Number: lm49370rl
• Description: Audio Sub-system With An Ultra Low Emi, Spread Spectrum, Class D Loudspeaker Amplifier, A Dual-mode Stereo Headphone Amplifier, And A Dedicated Pcm Interface For Bluetooth Transceivers
• Manufacturer: National Semiconductor Corporation

Bits
3:0
6:4
12.13 AGC_2 CONFIGURATION REGISTER
This register is used to control the LM49370's Automatic Gain Control.
Note 18: The AGC can be used to control the analog path of the microphone to the output stages or to optimize the microphone path for recording on the ADC.
When the analog path is used this bit should be set to ensure the target is tightly adhered to. If the ADC is the only destination of the microphone or the desired
analog mixer level is line level then AGC_TIGHT should be cleared, allowing greater dynamic rage of the recorded signal. For further details see the AGC
overview.
7
AGC_MAX_GAIN This programs the maximum gain that the AGC algorithm can apply to the microphone preamplifier.
AGC_TIGHT = 0
AGC_TIGHT = 1
AGC_DECAY
AGC_TIGHT
Field
This programs the speed at which the AGC will increase gains if it detects the input level is a quiet signal.
If set, the AGC algorithm controls the microphone preamplifier more exactly. (Note 18)
AGC_MAX_GAIN
AGC_TARGET
0100
AGC_DECAY
0000
0001
0010
0011
1101
1110
1111
2
000
001
010
011
100
101
110
111
000
001
010
011
100
101
110
111
000
001
010
011
100
101
110
111
to 1100
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
TABLE 15. AGC_2 (0x09h)
33
Description
Min Level
−10 dB
−12 dB
−14 dB
−16 dB
−18 dB
−20 dB
−10 dB
−12 dB
−14 dB
−16 dB
−18 dB
−20 dB
−6 dB
−8 dB
−6 dB
−8 dB
Max Preamplifier Gain
Step Time (ms)
14 dB to 30 dB
10 dB
12 dB
32 dB
34 dB
36 dB
1024
2048
4096
6 dB
8 dB
128
256
512
32
64
Max Level
−10 dB
−11 dB
−13 dB
−15 dB
−17 dB
−3 dB
−4 dB
−5 dB
−6 dB
−7 dB
−8 dB
−9 dB
−3 dB
−5 dB
−7 dB
−9 dB
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