LG KE820 Service Manual page 100

5.12.4 Checking PLL Control signals
Checking Points
R419 (RF_EN)
U402
R427 (RF_DATA)
Figure 7. Transceiver
Circuit Diagram
RF Transceiver
C418
0.1u
X1V5 VDDRX2V8
20
VDDRX1V5
U402
19 R414
VCO_RC
PMB6272
18 820
X2V8 VDDVCO2V8
17
X2V8 EN
16
VDDXO2V8
15
FSYS1
14
GND1
13
100p
C426
C427 1000p
R426
0
R427
0
Figure 8. Transceiver Circuit
R426 (RF_CLK)
R448
0
C419 C420 C421 C422
47n 0.1u 0.1u 0.1u
R419
0
C423 1000p
2V7_VCXO
R449
0
X401
R424
3 1
OUT VCONT
0
4 2
VCC GND
BT_CLK C431
26MHz
1uF
RF_CLK
RF_DA
Checking Flow
EN Signal is
OK ?
Yes
DA(Data) is
Normal
Yes
CLK(Clock) is
Normal
Yes
Control Signal is OK.
See next page to check
Mobile SW & FEM.
Waveform
RF_EN
26MHZ_MCLK
R425
C430
22p
Figure 9. PLL Control Waveform
- 101 -
5. Trouble shooting
No
Check U402
No
Check U402
No
Check U402
RF_EN
RF_CLK
RF_DATA