Motorola i897 - Frequency Generator (RF) Section

OVERVIEW: Frequency Generator (RF) Section
1.9 Frequency Generator (RF) Section
This section contains the following main components of the RF board:
• TCXO based Reference Oscillator Circuit.
• Host system clock synthesizer.
• (SLEDGEHAMMER) Phase Locked Loop synthesizers (Main & Escort).
• Main/RX Voltage Controlled Oscillator (VCO - U300). Note Main/RX VCO output used
as source to Main Prescaler input of SLEDGEHAMMER main synthesizer PLL.
All frequencies in the i897 originate from the 33.6 MHz reference frequency provided by
SLEDGEHAMMER synthesizer and the TCXO based reference oscillator circuit. The Y002
TCXO generates the 33.6 MHz signal, which is temperature compensated.
Figure 1-18 illustrates the frequency generator circuitry path:
U300
U600
Multi-Band Transceiver
Y002 TCXO
Bluetooth
Power Management IC /
Digital / Audio IC
DSP AFC
1702 - 1740 MHz
1870 - 1882 MHz
1804 -
1856
Loop Filter
÷ R
PFD
Loop
÷
÷ N
PFD
U400
U804
U700
U200 RX
Reference Oscillator
The 33.6 MHz reference is generated by temperature compensated crystal oscillator
(TCXO) and fed to SLEDGEHAMMER IC (CLKOUT) output provides a stable and
accurate 33.6 MHz reference frequency for the synthesizers. This 33.6 MHz signal is sent
to Bluetooth, SLEDGEHAMMER and ROADRUNNER as a reference. This reference is
divided down to a 4.2 MHz reference for JANUS (TCLK).
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6880401P59-O