LG Prada KE850 Service Manual page 100

5.13.4 Checking PLL Control signals
Checking Points
R416 (RF_EN)
U404
R424 (RF_DATA) R422 (RF_CLK)
Figure 7. Transceiver
RF Transceiver Circuit Diagram
VDDRX2V8
20
VDDRX1V5
U404
19
VCO_RC
MB6272
18
R414
VDDVCO2V8
17
Transceiver EN
16
VDDXO2V8
15
FSYS1
14
GND1
13
VRF2V7
R418
0
C444
100p R421 0
C445
NA
Figure 8. Transceiver Circuit
820
26M_BB
C433 470p
26MHz
VCC GND
4 2
R417
C442
OUT VCONT
0.1u
3 1
X401
10p
R422 0 C440
CLK
DA
R424 0
C446
NA
Checking Flow
EN Signal is OK?
DA(Data) is Normal?
CLK(Clock) is Normal?
Control Signal is OK.
See next page to check
Mobile SW & FEM.
Waveform
1.8K
AFC
Figure 9. PLL Control Waveform
- 101 -
5. Trouble shooting
No
Check U404
Yes
No
Check U404
Yes
No
Check U404
Yes
RF_EN
RF_CLK
RF_DATA