Only For Training And Service Purposes - LG GT500 Service Manual

3. TECHNICAL DESCRIPTION
3.3.4 Voice Call
A. Voice call Downlink Mode(Receiver, Speaker, Headset)
This section provides a detailed description of the Voice Call RX functions.
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 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 : BEARP/N Port
• Loud Speaker / Video Telephony Mode : AB3100 SPK Amp
•Headset Mode : Auxiliary audio amplifier
LGE Internal Use Only
Figure 3-3-4. Voice call Downlink Scheme
Receiver(32Ω)
AUDIO AMP(TPA6205) Speaker(8Ω)
AUXO1/2
AUDIO AMP(MAX9724D)
SPKR/N
Head Phone
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Only for training and service purposes