26 Mhz Reference Oscillator (Vcxo) - Nokia RH-29 Series Manual

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J612
VR1A
4.75V
VR5
2.8V
VIO
1.8V
VR3
2.8V

26 MHz reference oscillator (VCXO)

The 26 MHz reference oscillator (VCXO) is part of Mjoelner RF-ASIC (N601). It needs only
an external 26 MHz Xtal (B601) as external circuitry.
The reference oscillator has three functions:
• Reference frequency for the PLL synthesizer.
• System clock for BB (RFClk_I = 26 MHz).
• 26 MHz Reference clock (LPRFClk_I) for Bluetooth Module (N430) via
buffer V601.
For an error free initial synchronization, the 26MHz frequency of the VCXO must be
accurate enough. Therefore, a VCXO-calibration (cal) value is written via the serial Bus
into the RefOSCCAL register of Mjoelner and an additional bit in the RefOSCCntl register
of the Mjoelner. That is necessary for the rough calibration of the VCXO.
Issue 1 05/2004
Company Confidential
Figure 15: Mjoelner Can Test Points
VREF1
1.35V
Copyright © 2004 Nokia Corporation
Company Confidential
RH-29
6b - RF Troubleshooting
Page 9