Checking Vc-Tcxo Block - LG U250 Service Manual

4.4 Checking VC-TCXO Block

The reference frequency (19.2MHz) from X100 (VC-TCXO) is used in UMTS
TX part, GSM part and BB part.
VREG_TCXO_2.85V
TP1
TP4
C185
TCXO_PM
C187
RTR6275_TCXO
TP3
TP2
DSA321SCE-19.2M
NC3
7
NC4
8
OUTPUT
3
VCC
4
100p
1000p C188
Schematic of the VC-TCXO Block
TP1
Test Point of the VC-TCXO Block
- 77 -
4. TROUBLE SHOOTING
TCXO
X100
NC2
6
NC1
5
GND
2
100ohm
VCONT
1
19.2MHz
R128 100K
VCC
5
0.01u
2 4
U104 3
GND
TC7SH04FU
TP3
TP4
R124
TRK_LO_ADJ
TP2
C186
1000p
TCXO_BT