Cirrus Logic CS4297A - Manual (Page 23)

CS4297A
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4.7 Microphone Volume Register (Index 0Eh)
Mute Microphone Mute. Setting this bit mutes the MIC1 or MIC2 signal. The selection of the MIC1 or
MIC2 input pin is controlled by the MS bit in the General Purpose Register (Index 20h).
GN[4:0] Microphone Volume Control. The GN[4:0] bits are used to control the gain level of the Micro-
phone input source to the Input Mixer. Each step corresponds to 1.5 dB gain adjustment, with
01000 = 0 dB. The total range is +12 dB to -34.5 dB gain. See Table 3 for further details.
20dB Microphone 20 dB Boost. When ‘set’, the 20dB bit enables the +20 dB microphone boost block.
This bit allows for variable boost of 0 dB or +20 dB. Table 3 summarizes this behavior.
Default 8008h. This value corresponds to 0 dB gain and Mute ‘set’.
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
Mute 0 0 0 0 0 0 0 0 20dB 0 GN4 GN3 GN2 GN1 GN0
GN[4:0]
Gain Level
20dB = 0 20dB = 1
00000 +12.0 dB +32.0 dB
00001 +10.5 dB +30.5 dB
… … ...
00111 +1.5 dB +21.5 dB
01000 0.0 dB +20.0 dB
01001 -1.5 dB +18.5 dB
… … ...
11111 -34.5 dB -14.5 dB
Table 3. Microphone Input Gain Values
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CS4297A