Siemens A55 Repair Documentation

V1.20 Page 11 of 48 ICM MP CCQ GRM
A55/C55_Hitachi Company Confidential © Copyright Siemens AG 04/03
4.2.3 Synthesizer: LO2
The second local oscillator is required for transmitter operations only. It consists of a
PLL and a VCO which are integrated inside the Bright 4, and an external second order
loopfilter (R831; C830; C832). Before the VCO generated 640 or 656MHz signal
arrives at the modulator, it is divided by 8. So the resulting frequency after the IQ
modulator is 80/82MHz (dependent on the channel and band). Programming of the
LO2 PLL is done in the same way as described at the LO1 the tree-wire-bus
(EGOLD+ signals RFDATA; RFCLK; RFSTR.
(RF Control J15, J16, J17) is used. To ensure
the frequency stability, the 640MHz VCO signal is compared by the phase detector of
the 2
nd
PLL with the 26Mhz reference signal. The resulting control signal passes the
external loop filter and is used to control the 640/656MHz VCO.
The required voltage VCC_SYN is provided by the ASIC D361
Circuit diagram
Loop-filter LO2

Siemens A55 Specifications

General

Network	GSM 900 / 1800
Status	Discontinued
Weight	84 g (2.96 oz)
SIM	Mini-SIM
Display Type	Monochrome graphic
Call Records	10 dialed, 10 received, 10 missed calls
Loudspeaker	No
3.5mm Jack	No
Messaging	SMS
Java	No
Stand-by	Up to 250 h
Talk time	Up to 5 h
WAP	No
GPRS	No
Clock	Yes
Alarm	Yes
Calculator	Yes
Calendar	Yes
Announced	2003
Alert Types	Vibration; Downloadable monophonic ringtones
Games	Stack Attack
Battery Type	Removable Li-Ion battery
Resolution	101 x 64 pixels