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TDMA M3090/M3097:
OSC_DIS
RX_2.75
AFC
Description
The refere nce oscillator U150, operating at 19.44MHz, provides a "reference fre quency" fo r the RF synthesizers and various logic circuits.
The OSC_DIS line which is controlled by U1000 (CPU) is used to turn off U150 during sleep mode. The OSC_DIS line switches Q151 on or off, controllin g the supply
voltage to U150 and Q152.
U201 (DCI) can "fine tune" U150 via the AFC line. Tuning of the reference oscillator is needed to synchronize frequencies with the cellular base station, therefore, the
signal received from the base will be used to determine the correc t reference frequ ency.
The output of U150 is split into two signals. RF_19.44MHz is used for the RF frequency reference. Output 19.44MHz is amplified by Q152 and then sent to the logic
section for logic clock synchronization.
Reference Oscillator
Q151
U150
Q152
19.44MHZ
RF_19.44MHZ
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