LG TracFone LG840G Service Manual page 38

3. TECHNICAL BRIEF
3.5.6 Internal base band functions
Several baseband circuits within the QSC6270 device provide functions that are necessary only to make the device ope
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ate properly — these functions are not generally used directly by other handset circuits and functions.
* PLLs and clock generation
* Modes and resets
* Security
* Qfuse
* JTAG/ETM
The clock block includes two PLLs, all phase-locked to the TCXO signal. These PLLs generate several different stable, low-
jitter clock signals that are distributed throughout the QSC device and to external components as needed.
All the required WCDMA, GSM, GPS(only QSC6270), ARM, QDSP, and most peripheral clocks are derived in some way from
the TCXO (or XO) source for their operating modes, plus the 32.768 kHz oscillator for their sleep modes
External clocks
PLL0
Clock
Clock
PLL1
source
generators
select
TCXO
SLEEP_CLK
Clocks block
Figure 3.5.6 Clock block basic architecture of QSC6270
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Only for training and service purposes