lm4935rlx National Semiconductor Corporation, lm4935rlx Datasheet - Page 40

• Manufacturer Part Number: lm4935rlx
• Description: Audio Sub-system With Dual-mode Stereo Headphone And Mono High Efficiency Loudspeaker Amplifiers And Multi-purpose Adc
• Manufacturer: National Semiconductor Corporation

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Bits
12.0 Status & Control Registers
12.18 SIDETONE ATTENUATION REGISTER
This register is used to control the analog sidetone attenuation. (Note 20)
Note 20: An active SIDETONE path to an audio output 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 potential pop noises, it is recommended to set SIDETONE_ATTEN to ’0000’ until DC points have stabilized whenever the SIDETONE path is used.
3:0
SIDETONE_
ATTEN
Field
Programs the attenuation applied to the microphone preamp output to produce a sidetone signal.
SIDETONE_ATTEN
0101
1011
TABLE 19. SIDETONE (0x0Dh)
0000
0001
0010
0100
0011
2
2
to 1010
to 1111
2
2
2
2
2
(Continued)
2
2
40
Description
−18 dB to −3 dB
Attenuation
−30 dB
−27 dB
−24 dB
−21 dB
0 dB
-Inf