IA4420 Datasheet, PDF (25/29 Pages) List of Unclassifed Manufacturers – Universal ISM Band FSK Transceiver

IA4420
CRYSTAL SELECTION GUIDELINES
The crystal oscillator of the IA4420 requires a 10 MHz parallel mode crystal. The circuit contains an integrated load capacitor in order to
minimize the external component count. The internal load capacitance value is programmable from 8.5 pF to 16 pF in 0.5 pF steps. With
appropriate PCB layout, the total load capacitance value can be 10 pF to 20 pF so a variety of crystal types can be used.
When the total load capacitance is not more than 20 pF and a worst case 7 pF shunt capacitance (C₀) value is expected for the crystal, the
oscillator is able to start up with any crystal having less than 300 ohms ESR (equivalent series loss resistance). However, lower C₀ and ESR
values guarantee faster oscillator startup.
The crystal frequency is used as the reference of the PLL, which generates the local oscillator frequency (f_LO). Therefore f_LO is directly
proportional to the crystal frequency. The accuracy requirements for production tolerance, temperature drift and aging can thus be determined
from the maximum allowable local oscillator frequency error.
Whenever a low frequency error is essential for the application, it is possible to “pull” the crystal to the accurate frequency by changing the
load capacitor value. The widest pulling range can be achieved if the nominal required load capacitance of the crystal is in the “midrange”,
for example 16 pF. The “pull-ability” of the crystal is defined by its motional capacitance and C₀.
Maximum XTAL Tolerances Including Temperature and Aging [ppm]
Bit Rate: 2.4kbps
30
45
315 MHz
25
50
433 MHz
20
30
868 MHz
10
20
915 MHz
10
15
Bit Rate: 9.6kbps
30
45
315 MHz
20
50
433 MHz
15
30
868 MHz
8
15
915 MHz
8
15
Bit Rate: 38.3kbps
30
45
315 MHz don't use
7
433 MHz don't use
5
868 MHz don't use
3
915 MHz don't use
3
Deviation [+/- kHz]
60
75
90
105
120
75
100
100
100
100
50
70
90
100
100
25
30
40
50
60
25
30
40
50
50
Deviation [+/- kHz]
60
75
90
105
120
70
75
100
100
100
50
70
80
100
100
25
30
40
50
60
25
30
40
50
50
Deviation [+/- kHz]
60
75
90
30
50
75
20
30
50
10
20
25
10
15
25
105
120
100
100
75
75
30
40
30
40
25