CM108 Datasheet, PDF (17/29 Pages) C-Media Electronics – USB Audio I/O Controller

CM108
Integration Dual DAC, Earphone Driver, ADC,
Microphone Booster, PLL, Regulator, and USB Transceiver
7.2 Jumper Pins and Mode Setting:
Jumper pins can set the configuration of CM108. These jumper pin settings affect both
USB descriptors and USB audio topology.
7.2.1 MODE Pin and MSEL Pin
If MODE pin is pulled high (Speaker Mode), a playback only function is activated and
there is no recording function declared to the host. At this setting, MSEL pin is ignored and
only one input terminal, one output terminal and one feature unit is declared in USB audio
topology.
If MODE pin is pulled low (Headset Mode), a full duplex playback and recording function is
reported to the host. MSEL pin setting activates one mixer unit and one feature unit.
When MSEL = 1, Mixer is enable (AA-Path enable), but with default mute setting;
When MSEL = 0, Mixer is disable (AA-Path disable).
The above USB audio topology (7.1.4) is an example of headset mode with Mixer enable.
7.2.2 MODE Pin and PWRSEL Pin
PWRSEL pin affects the power configuration of CM108; together with MODE pin totally
4 combinations are programmable.
Combinations
PWRSEL
3.3V
GND
3.3V
MODE
GND
Speaker Mode:
Headset Mode:
Playback Only
Playback + Recording
(Self Power with 100mA) (Bus Power with 100mA)
Speaker Mode:
Headset Mode:
Playback Only
Playback + Recording
(Bus Power with 500mA) (Bus Power with 500mA)
USB Audio Topology Diagram
7.2.3 VSEL Pin
VSEL jumper pin sets the output voltage swing. When VSEL is connected to 5V, output
voltage swing is 3.5Vpp; when VSEL is connected to ground, output voltage is 2.5Vpp.
Date: Nov/01/2004
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Version: 1.5