LG -T370 Service Manual page 29

3. TECHNICAL BRIEF
3. TECHNICAL BRIEF
input to system
control unit
reset for external
for example µC
components
reset
resetout_o
reset_postscu_n_o
lsoation
reset_pmu_n_o
&LS
reset_pmu_n_o
open drain
pad driver
VDD_VDIG1
0k
ESD ESD
VPMU voltage domain
VDD_VRTC
Figure 3.2.4 PMU, CGU and External Reset
3.2.8 Sysclock Switching
The PMU controls the rf_sysclk_en signal of the DCXO in the RF macro. During startup the PMU enables the
DCXO. After the system is running the DCXO is controlled by the SCU of the baseband by using the
vcxo_enable signal. This is handled by a dedicated logic in the PMU, see Figure 21. As long as
rf_sysclk_en_pmu, the output of the PMU state-machine is high, vcxo_enable controls the rf_sysclk_en signal
to the RF. If rf_sysclk_en_pmu is low, the DXCO is switched off, independent from vcxo_enable.
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Only for training and service purposes