Lte Vcxo Trouble - LG FM300 Service Manual

4.11 LTE VCXO Trouble

The reference frequency(19.2MHz) from X200(VCTCXO) is used for system clock. The AFC is calibrated to
generate the 19.2MHz with very low ppm.
The AFC voltage is about 1.4V at R205(TP1) point and VCC voltage is about 2.8V at C201.(TP2)
The 26MHz must be checked at C202.(TP3)
TP1 TP1
TP1
R200 100
AFC_OUT
C203
33n
LGE Internal Use Only
2V8_TCXO
X200
TG-5025CG-19_2M
1 4
TP2
VC VCC
5 6
TP1 TP2
2 3
GND OUT
19.2MHz
C204
100n
TP3
C201
Figure 4.2
- 56 -
4. TROUBLE SHOOTING
R203 200K
VCC
5
10n
C201
2 4
TP3
U200
3
GND
NL17SZ04XV5T2G
TP2 TP3
TP2
10n
C205
TCXO_IN
R200
TP1
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4. TROUBLE SHOOTING
2V8_TCXO
100n
C200
R202 33
REF_CLK_OUT
Only for training and service purposes