W681308DG Datasheet, PDF (46/64 Pages) Nuvotem Talema – W681308 USB Audio Controller from Nuvoton integrates fast 8051 Microcontroller Unit (MCU)

W681308
XXXX PRODUCT DESCRIPTION
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.
ƒ Auxiliary Input Mode
For non-microphone applications one or more Auxiliary inputs can be connected to the MCP pin as shown in
Figure 11 below. The MIC_RES register should be set to open in order to disconnect the microphone bias. For the gain
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.
MIC_BIAS[2:0]
0x1488
W681308
MIC_RES[7:4]
0x1488
=‘0100’
Auxiliary Input Mode
0x1489
MIC_MODE[2:0]=‘101’
Cs₁
Rs₁
MCP
+
To ADC
+
Vs
-
Cs_n
Rs_n
+
Vs_n
-
MIC_GAIN[7:4]
0x1489
-
Rinternal
0x1489
MCO
RGND
250 Ohm
VADC
= − ^{REXT+ 250}
VS _'101'
RS
REXT > 20 kΩ
CS = ¹
40 ⋅ π⋅ RS
Figure 11 Microphone Auxiliary Input Mode
46
Rev1.2