LG U8120 Service Manual page 55

3. TECHNICAL BRIEF
The voice decoder accepts a serial input stream of linear PCM coded speech. The receive band-pass
filter is the next step in the CODEC receive path. Following the filter is the DAC, followed by a PGA
enabling to adjust or trim the circuit in the product for different sensitivity of the earphone and spread in
the RX path. The final step in the receive path is the earphone amplifier and the auxiliary output.
The auxiliary audio amplifier is intended to drive low impedance headphones. The earphone
amplifier and the auxiliary audio outputs can be powered down (muted) via I2C. Both the earphone
driver and one of the auxiliary drivers can simultaneously provide an output signal during voice
decoding.
• Receiver Mode : Earphone amplifier → BEARP/N Port → Receiver(32Ω)
• Loud Speaker Mode : Earphone amplifier → BEARP Port → Analog S/W(ADG702) →
•Video Telephony Mode : Earphone amplifier → BEARP Port → Analog S/W(N2603) →
• Headset Mode : Auxiliary audio amplifier → AUXO1/2 →
TJATTE2 IN (AFMS_R_INT/AFMS_L_INT) →
TJATTE2 OUT(AFMS_R/AFMS_L) → Head Phone
Speaker Phone Mode has two GPIO switching control ports. One is SPKMUTE and the other is
AMPCTRL. SPKMUTE controls analog switch( ADG702) and AMPCTRL controls shutdown of
AUDIOAMP(LM4894IBP). Video Telephony Mode has same paths with Loud Speaker Mode.
Mode
Receiver
Headset
Loud Speaker
Video Telephony
* SPKMUTE; MARITA GPIO36
* AMPCTRL; MARITA GPIO06
AUDIO AMP(LM4894IBP) → Speaker(8Ω)
AUDIO AMP (LM4894IBP) → Speaker(8Ω)
SPKMUTE
Table Speaker Phone Mode GPIO control state
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High
High
Low
Low
AMPCTRL
Low
Low
High
High