xe1202 ETC-unknow, xe1202 Datasheet - Page 25

• Manufacturer Part Number: xe1202
• Description: Low-power, Integrated Uhf Transceiver
• Manufacturer: ETC-unknow

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:
(*) The on-chip oscillator is implemented in two selectable versions: 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 a higher amplitude for the internal signal with a slightly
lower consumption.
The electrical specifications given in section 3.2.2 are valid provided the crystal satisfies the specifications given in
table 5.
For less demanding applications in term of signal bandwidth and/or temperature range, it is possible to use 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.
XE1202 can be used with reference crystal operating on its 3
a) the oscillator start-up time is higher than in fundamental mode; and b) an extra 1.5k to 16k ohm external resistor
has to be placed in parallel to the crystal. In this case, the crystal should have Cload = 8 to 10pF, Rm < 60 ohm, C0
< 7pF.
6.6 Decoupling capacitances
A decoupling capacitance will be placed between each VDD pins and the ground VSS. These five capacitances
must have the following characteristics:
25
Name
Fs
CL
Rm
Cm
C0
fs(0)
fs( T)
fs( t)
Description
Nominal frequency
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
Name
Cci
Table 5 Crystal characteristics
Typ. value
100 nF
Min. value
-
-
-
-
-
-
-
-
rd
harmonic at 39.00 MHz. This has 2 consequences:
Tolerance
10 %
Typ. value
39.0 MHz
(fundamental)
8 pF (*)
-
-
-
-
-
-
Data Sheet
XE1202
Max. value
-
-
40
30 fF
7 pF (*)
10 ppm
10 ppm
5 ppm
D0211-105