lm49370rl National Semiconductor Corporation, lm49370rl Datasheet - Page 36

• 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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Bits
3:0
12.16 MIC_1 CONFIGURATION REGISTER
This register is used to control the microphone configuration.
Note 20: On changing INT_EXT from internal to external note that the dc blocking cap will not be charged so some time should be taken (300 ms for a 1 µF cap)
between the detection of an external headset and the switching of the output stages and ADC to that input to allow the DC points on either side of this cap to
stabilize. This can be accomplished by deselecting the microphone input from the audio outputs and ADC until the DC points stabilize.
An active MIC path to CPOUT or the ADC may result in the microphone DC blocking caps causing audio pops under the following situations:
1) Switching between internal and external microphone operation while in chip modes '10' or '11'.
2) Toggling in and out of powerdown/standby modes.
3) Toggling between chip modes '10' and '11' whenever external microphone operation is selected.
4) The insertion/removal of a headset while in chip modes '10' or '11' whenever external microphone operation is selected.
To avoid these potential pop issues, it is recommended to deselect the microphone input from CPOUT and ADC until the DC points stabilize.
4
5
6
PREAMP_GAIN
INT_SE_DIFF
MIC_MUTE
INT_EXT
Field
This programs the gain applied to the microphone preamplifier if the AGC is not in use.
If set, the microphone preamplifier is muted.
If set, the internal microphone is assumed to be single ended and the negative connection is connected
to the ADC common mode point internally. This allows a single-ended internal microphone to be used.
If set, the single ended external microphone is used and the negative microphone input is grounded
internally, otherwise internal microphone operation is assumed. (Note 20)
PREAMP_GAIN
0100
0000
0001
0010
0011
1101
1110
1111
2
TABLE 17. MIC_1 (0x0Bh)
to 1100
2
2
2
2
2
2
2
2
36
Description
14 dB to 30 dB
10 dB
12 dB
32 dB
34 dB
36 dB
Gain
6 dB
8 dB