Multi Port Switch - LG KE970 Service Manual

3. TECHNICAL BRIEF
3.13.2. Microphone with gain switching circuit
When a call is established, MICBIAS signal goes up to '2.5V' in the MKE970. PMB8876(S-Gold2)
provides both 2.0V and 2.5V for MICBIAS to circuit designer. VA01, VA02 are employed to enhance
ESD immunity.
MICROPHONE
MIC1_P
MIC1_N
VMICP
VMICN

3.14. Multi port switch

Multi port switch has employed to decrease MMI(Multi Media Interface) connector's pin number. USB,
USART, Remote controlled Headset is connected via this multi port switch. When USB VBUS voltage
is detected Multi port 0 and 1 is connected to USB_DP and USB_DM each. If the remote controlled
headset is plugged into MMI connector, then multi port 0 and 1 in go through REMOTE_INT and
REMOTE_ADC.
Table 9 Multi port switch truth table
VBUS_USB='L'
JACK_DETECT='L'
Pin6 REMOTE_INT
Pin7 REMOTE_ADC
C501 C502
15p
33p
R503 220 R504
C506
1u
R505 220 R507
R506
NA
Figure 22 Microphone circuit
VBUS_USB='L'
JACK_DETECT='H'
- 48 -
VA501
ESD9X5.0ST5G
1
C503 MIC501
2 OSF213-42DC
47p
VA502
ESD9X5.0ST5G
1K
1K
TXD
RXD
VBUS_USB='H'
USB_DP
USB_DM