lm49370rl National Semiconductor Corporation, lm49370rl Datasheet - Page 32

• 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

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3:1
7:5
Bit
s
0
4
12.12 AGC_1 CONFIGURATION REGISTER
This register is used to control the LM49370's Automatic Gain Control. (Note 17)
Note 17: See the AGC overview.
NOISE_GATE_ON If set, signals below the noise gate threshold are muted.The noise gate is only activated after a set period of
AGC_TARGET
AGC_ENABLE
NOISE_
THRES
GATE_
Field
If set, the AGC controls the analog microphone preamplifier gain into the system. This feature is useful for
microphone signals that are routed to the ADC.
This programs the target level of the AGC. This will depend on the expected transients and desired headroom.
Refer to AGC_TIGHT (bit 7 of 0x09h) for more detail.
signal absence.
This field sets the expected background noise level relative to the peak signal level. The sole presence of
signals below this level will not result in an AGC gain change of the input and will be gated from the ADC
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
AGC_TARGET
000
001
010
011
100
101
110
111
000
001
010
011
100
101
110
111
TABLE 14. AGC_1 (0x08h)
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
32
Description
Target Level
−10 dB
−12 dB
−14 dB
−16 dB
−18 dB
−20 dB
−72 dB
−66 dB
−60 dB
−54 dB
−48 dB
−42 dB
−36 dB
−30 dB
−6 dB
−8 dB
Level