XE1203 Datasheet, PDF (35/37 Pages) List of Unclassifed Manufacturers – Low-Power, integrated UHF transceiver

Data Sheet
XE1203
6.5 REFERENCE CRYSTAL FOR THE FREQUENCY SYNTHESIZER
For narrow band applications, where users select the lowest frequency deviation and the narrowest baseband
filter, the crystal for reference oscillator of the frequency synthesizer must have the following characteristics:
Name
Fs
CL
Rm
Cm
C0
∆fs(0)
∆fs(∆T)
∆fs(∆t)
Description
Nominal frequency
Min. value
-
Load capacitance for fs (on-chip) -
Motional resistance
-
Motional capacitance
-
Shunt capacitance
-
Calibration tolerance at 25 °C
-
Stability over temperature range -
(-40 °C to 85 °C)
Aging tolerance in first 5 years
-
Typ. value
39.0 MHz
(fundamental)
8 pF (*)
-
-
-
-
-
-
Table 5 Crystal characteristics
Max. value
-
-
40 Ω
30 fF
7 pF (*)
10 ppm
10 ppm
5 ppm
(*) The on-chip oscillator mode is user-defined by programming ADParam_Xsel: the first for CL = 8 pF and C0 = 7
pF, and the second for CL = 8 pF and C0 = 3 pF; the latter will allow higher amplitude for the internal signal with a
slightly lower consumption.
The electrical specifications given in section 3.2.2 are valid for a crystal having the specifications given in table 5.
For applications requiring less frequency stability in terms of signal bandwidth and/or temperature range, it is
possible to use a crystal with larger values for ∆fs(0), ∆fs(∆T), and/or ∆fs(∆t). In this case foffset + BWssb should
be lower than BWfilter, where foffset is the offset (error) on the carrier frequency (the sum of ∆fs(0), ∆fs(∆T), and/or
∆fs(∆t)), BWssb is the single side-band bandwidth of the signal, and BWfilter is the single side-band bandwidth of
the base-band filter.
The overtone crystal usage can result higher oscillator start-up time than fundamental mode. The overtone crystal
should be designed for Cload = 8 to 10pF and has parameters of Rm < 60 ohm, C0 < 7pF.
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D0308-214