w681308 Winbond Electronics Corp America, w681308 Datasheet - Page 46

• Manufacturer Part Number: w681308
• Description: Usb Audio Controller
• Manufacturer: Winbond Electronics Corp America

The current gain mode uses the same programmable microphone bias voltage and resistor as the voltage gain mode. The
gain is set by either the internal gain resistor or an external resistor, depending on the MIC_MODE setting. Since the current
gain mode is using a single resistor, the gain accuracy is limited. However, large gain can be achieved. Note that a 250Ohm
ESD protection resistor is connected to the MCO pin. This resistor should be considered when calculating the gain.
For non-microphone applications one or more Auxiliary inputs can be connected to the MCP pin as shown in
Figure
setting it is advised to use external gain resistors only for optimal matching and accuracy. The 250Ohm ESD protection
resistor should be considered again when calculating the gain. Note that for this mode the RGND pin is tied to the external
supply ground. A clean ground reference should be used for this.
+
+
Vs
Vs
-
-
Auxiliary Input Mode
11
+
+
Vs
Vs
-
-
below. The MIC_RES register should be set to open in order to disconnect the microphone bias. For the gain
n
n
Cs
Cs
Cs
Cs
1
1
n
n
Rs
Rs
Rs
Rs
n
n
1
1
RGND
MCP
MCP
MCO
MCO
Figure 11 Microphone Auxiliary Input Mode
MIC_RES[7:4]
MIC_RES[7:4]
=‘0100’
=‘0100’
0x1488
0x1488
250 Ohm
250 Ohm
MIC_GAIN[7:4]
MIC_GAIN[7:4]
XXXX PRODUCT DESCRIPTION
0x1489
0x1489
46
MIC_BIAS[2:0]
MIC_BIAS[2:0]
0x1488
0x1488
Rinternal
Rinternal
+
+
-
-
0x1489
0x1489
Auxiliary Input Mode
Auxiliary Input Mode
MIC_MODE[2:0]=‘101’
MIC_MODE[2:0]=‘101’
W681308
W681308
R
R
C
C
V
V
V
V
EXT
EXT
S
S
0x1489
0x1489
ADC
ADC
=
=
S
S
>
>
40
40
'
'
101
101
20
20
'
'
⋅
⋅
1
1
π
π
=
=
kΩ
kΩ
⋅
⋅
−
−
R
R
S
S
R
R
To ADC
To ADC
EXT
EXT
R
R
+
+
S
S
250
250
W681308
Rev1.2