Vctcxo; Transmitter Part - LG MG810c Service Manual

3. H/W Circuit Description

3.3.1. VCTCXO

The VCTCXO module supply 26MHz reference clock and controlled by AFC input to generate a
precise system reference clock adjustment.
The 26 MHz clock(X500) consists of a TCXO(Temperature Compensated Crystal Oscillator) which
oscillates at a frequency of 13 MHz. It is used within the TRF6151C RF Main Chip, BB Analog chip-
set(IOTA), Digital chip-set(Calypso Lite).
AFC

3.4 Transmitter Part

The Transmitter part contains SI4210[U401] active parts, Power Amp Module[U400] and Antenna
Switch Module[FL400]. The transmit section of SI4210[U401] consists of an I/Q baseband pconverter,
an offset phaselocked loop (OPLL) and two 50 ohm output buffers that can drive external power
amplifiers. The RF GMSK outputs from the transmit VCO are fed directly to the RF power amplifiers.
The peak output power and the profile of the transmitted burst are controlled by means of incorporated
power control circuits inside of PA and DAC output. from the Baseband Controller. The PA outputs
pass to the antenna connector via Antenna Switch Module.
RF2.85V
X401 26MHz
R425
1 3
VCONT OUT
15K
2 4
GND VCC
C431 C430
1000p 1u
Figure 4. VC-TCXO Circuit
Figure 3. TRANSMITTER PART Block Diagram
RF2.85V
R550
100K
C428 C999
1000p 1000p
C429
1000p
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BT_26MHZ
TCXO_OUT