26 Mhz Clock (Vctcxo, X500); Power Supplies For Rf Circuits (Rf Ldo, U503) - LG C2100 Service Manual

3. TECHNICAL BRIEF

3.3 26 MHz Clock (VCTCXO, X500)

The 26 MHz clock(X500) consists of a TCXO(Temperature Compensated Crystal Oscillator) which
oscillates at a frequency of 26 MHz. It is used within the Si4205, digital base band chipset (U101,
AD6527)
C528
100p

3.4 Power Supplies for RF Circuits (RF LDO, U503)

Two regulators are used for RF circuits. One is MIC5255 (U503), and the other is one port of AD6537B
(U102).
MIC5255 (U503) supplies power to transceiver (SI4205, U505). One port of AD6537B supplies power
to VCTCXO (X500). Main power (VBAT) from battery is used for PAM (SKY77325, U501) because
PAM requires high power.
Supplier
U503(VRF)
U102(VVCXO)
Battery(VBAT)
RF PARTS
Figure 3-6 VCTCXO CIRCUIT DIAGRAM
2V75_VVCXO
R510
3
OUT
100
4
VCC
C539
2.2u
Table 3-2 RF POWER SUPPLIERS
Voltage
2.85 V
2.75 V
3.4 ~ 4.2 V
Figure 3-7 RF LDO CIRCUIT DIAGRAM
RF2.85V
U503
5
OUT
GND
4
BYP
C536
C535
4.7u 22n MIC5255-2.85BM5
(1608)
X500
1
VCONT
2
GND
C540
0.1u
26MHz
Powers
U505, U501
X501
U501, U503
RF_LDO
VBAT
1
IN
2
3
EN
C529
4.7u
(1608)
- 22 -
R515
AFC
10K
enabled signal
CLKON
CLKON