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4.2 Frequency generation
4.2.1 Synthesizer: The discrete VCXO (26MHz)
The A55/C55 mobile is using a reference frequency of 26MHz for the Hitachi chip set.
The generation of the 26MHz signal is done via a discrete "Colpitts" VCXO. This
oscillator consists mainly of:
A 26MHz crystal
An oscillator switch
A capacity diode
TP (test point) of the 26MHz signal is the TP 1501
The oscillator output signal 26MHz_RF is directly connected to the BRIGHT IC
38)
to be used as reference frequency inside the Bright (PLL). The signal leaves the
Bright IC as BB_SIN26M at pin 36 to be further used from
the EGOLD+
(D100
(functional T3))
Bright 4
To compensate frequency drifts (e.g. caused by temperature) the oscillator frequency
is controlled by the (AFC) signal, generated through the internal EGOLD+
) PLL via the capacity diode V951. Reference for the "EGOLD-PLL" is the
(functional U5)
base station frequency. To compensate a temperature caused frequency drift, the
temperature-depending resistor
temperature. The measurement result
via
R138
as the signal TENV.
Interface P3)
The required voltage
VCC_SYN
V1.20
A55/C55_Hitachi
Z950
V950
V951
.
R959
is placed near the VCXO to measure the
TVCXO
is provided by the ASCI
Page 7 of 48
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is reported to the EGOLD+
D361
(pin
(D100
(Analog
ICM MP CCQ GRM
04/03
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