Clock Distribution - Nokia 2608 Service Manual

RM-376
System Module and User Interface

Clock distribution

The SC6020 derives its internal clock from two clock inputs, TCXO and SLEEP_CLK. Q
The main clock signal for the baseb and generates from TCXO (Temperatu re-compensated crystal oscillator).
T he QSC6020's TCXO clock input supports the frequency 19.2 MHz +/-2ppm. The SLEEP_CLK provides a 32.768
kHz +/-20ppm clock source to drive the MSM controller into sleep mode. At this mode, most of the MSM is
powered down and the TCXO is disabled.
System Clocks
The power management circuits include several clock circuits whose outputs are used for general
housekeeping functions and elsewhere within the handset system. These circuits include the 19.2 MHz TCXO
source, controller, and buffers; RC oscillator; 32 kHz crystal oscillator; SLEEP clock; and SMPS clock. The baseline
configurations are shown in Figure 47, but some circuits offer multiple implementation options. Detailed
descriptions of all these functions and their options (where applicable) are presented in the following
subsections.
Figure 8 TCXO and SLEEP_XTAL Block Diagram
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