AD1985

Rev. A | Page 19 of 48

Phone_In Volume Register (Index 0x0C)

Reg Num

Name

D15

D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4

D3

D2

D1

D0

Default

0x0C

Phone_In Volume

PHM X

X

X

X

X

X

X

X

X

X

PHV4 PHV3 PHV2 PHV1 PHV0 0x8008

PHV[4:0]

Phone Volume. Allows setting the phone volume gain/attenuator to one of 32 levels. The LSB represents 1.5 dB,

and the gain range is +12 dB to –34.5 dB. The default value is 0 dB, with mute bit enabled.

PHM

Phone Mute. When this bit is set to 1, the Phone channel is muted.

Volume Settings for Phone and MIC

Control Bits D[4:0]

Phone (0x0C) and MIC (0x0E)

D15

Write

Readback

Function

0

0 0000

0 0000

12 dB Gain

0

0 1000

0 1000

0 dB Gain

0

1 1111

1 1111

–34.5 dB Gain

1

x xxxx

x xxxx

–∞ dB Gain, Muted

Note that the x in the above table is a wild card, meaning the value has no effect.

Microphone Volume Register (Index 0x0E)

Reg Num

Name

D15

D14 D13 D12 D11 D10 D9 D8 D7 D6

D5 D4

D3

D2

D1

D0

Default

0x0E

MIC Volume

MCM

X

X

X

X

X

X

X

X

M20 X

MCV4

MCV3

MCV2

MCV1

MCV0

0x8008

This register controls the volume, gain boost, and mute for the gain/attenuators on both the MIC1 and MIC2 paths to the mixer. There is

no separate control for left and right on this path. The signal paths must be identical, hence the single control for both.

MCV[4:0]

MIC Volume. Allows setting the MIC volume gain/attenuator to one of 32 levels. The LSB represents 1.5 dB, and the

gain range is +12 dB to –34.5 dB. The default value is 0 dB, with mute enabled.

M20

MIC Gain Boost. This bit allows setting additional MIC gain to increase the microphone sensitivity. Gain is applied

to the microphone path to both the analog mixer and the ADC(s).

The nominal gain boost by default is +20 dB; however, Bits D0 and D1 (MBG[1:0]) on the Miscellaneous Control Bits

Register (0x76), allow changing the gain boost to +10 dB or +30 dB, if necessary.

0 = Disabled; Gain = 0 dB.

1 = Enabled; Default Gain = +20 dB (see Register 0x76, Bits D0 and D1).

MCM

MIC Mute. When this bit is set to 1, both channels are muted.