LG LG-YD636, Service Manual

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1.4 Description of Frequency Synthesizer Circuit
1.4.1 Voltage Control Temperature Compensation Crystal Oscillator
The temperature range that can be compensated by VC-TCXO which is the reference frequency
generator of a mobile station is -30~+80 C.
The VC-TCXO receives frequency tuning signals called TRK_LO_ADJ from MSM as 0.5V~2.5V DC
via R and C filters in order to generate the reference frequency of 19.2MHz and input it into the
frequency synthesizer of UHF band. Frequency stability depending on temperature is ±2.0 ppm.
2. Digital/Voice Processing Part
2.1 Overview
The digital/voice processing part processes the user's commands and processes all the digital and
voice signal processing in order to operate in the phone. The digital/voice processing part is made up
of a keypad/LCD, receptacle part, voice processing part, mobile station modem part, memory part,
and power supply part.
2.2 Configuration
2.2.1 Keypad/LCD and Receptacle Part
This is used to transmit keypad signals to MSM6025. It is made up of a keypad backlight part that
illuminates the keypad, LCD part that displays the operation status onto the screen, and a receptacle
that receives and sends out voice and data with external sources.
2.2.2 Voice Processing Part
The voice processing part is made up of an audio codec used to convert MIC signals into digital voice
signals and digital voice signals into analog voice signals, amplifying part for amplifying the voice
signals and sending them to the ear piece, amplifying part that amplifies ringer signals coming out
from MSM6025, and amplifying part that amplifies signals coming out from MIC and transferring them
to the audio processor.