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V 1.0 Page 8of 52 ICM MP CCQ GRM
SL55
Company Confidential © Copyright Siemens AG
06/03
Circuit diagram
4.2.2 Synthesizer: LO1
The local oscillator (LO1) consists of a PLL inside the Smarti DC (D720), an external loop
filter. The VCO is build in.
The first local oscillator is needed to generate frequencies which enables the transceiver
IC to demodulate the receiver signal and to perform the channel selection in the TX part.
The LO1/PLL part is switched on with PLLON (
pin 5) from the EGOLD+ (D171 (GSM TDMA
Timer F16))
. The PLL settings are programmed by the 3 wire bus RFCLK (pin 1), RFDATA
(
pin2) and RFSTR (pin3). The LO frequency is 4 times the RX/TX frequency for EGSM 900
and 2 times for GSM1800/1900.
This LO1 frequency range
The required voltage VRREGRF1 is provided by the ASIC D361
from EGOLD
to EGOLD+
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