Siemens S55 - Overview of Phone

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S55/S57 Company Confidential © Copyright Siemens AG 12/02
4.1 Power Supply RF-Part
The voltage regulator for the RF-part is located inside the ASIC D361.(see chapter
5.2).It generates the required 2,8V “RF-Voltages” named VCC2_8 and VCC_SYN .
The voltage regulator is activated as well as deactivated via SLEEPQ
(TDMA-Timer H16)
and VCXOEN_UC (Miscellaneous R6) provided by the EGOLD+. The temporary
deactivation is used to extend the stand by time.
Circuit diagram
Between Power Supply ASIC and RF-Part a resistor based interface consisting of
resistor R841 for VCC2_8 and R843 for VCC_SYN is used .
V
CC2
_
8
V
CC
_
SYN