Datasheet
LM49370
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SNAS356D –FEBRUARY 2007–REVISED MARCH 2012
Table 14. AGC_1 (0x08h) (continued)
Bit Field Description
s
7:5 NOISE_ This field sets the expected background noise level relative to the peak signal level. The sole presence of
GATE_ signals below this level will not result in an AGC gain change of the input and will be gated from the ADC
THRES output if the NOISE_GATE_ON is set. This level must be set even if the noise gate is not in use as it is
required by the AGC algorithm.
NOISE_GATE_THRES Level
000
2
−72 dB
001
2
−66 dB
010
2
−60 dB
011
2
−54 dB
100
2
−48 dB
101
2
−42 dB
110
2
−36 dB
111
2
−30 dB
AGC_2 CONFIGURATION REGISTER
This register is used to control the LM49370's Automatic Gain Control.
Table 15. AGC_2 (0x09h)
Bits Field Description
3:0 AGC_MAX_GAIN This programs the maximum gain that the AGC algorithm can apply to the microphone preamplifier.
AGC_MAX_GAIN Max Preamplifier Gain
0000
2
6 dB
0001
2
8 dB
0010
2
10 dB
0011
2
12 dB
0100
2
to 1100
2
14 dB to 30 dB
1101
2
32 dB
1110
2
34 dB
1111
2
36 dB
6:4 AGC_DECAY This programs the speed at which the AGC will increase gains if it detects the input level is a quiet signal.
AGC_DECAY Step Time (ms)
000
2
32
001
2
64
010
2
128
011
2
256
100
2
512
101
2
1024
110
2
2048
111
2
4096
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