Si4020
23
CRYSTAL SELECTION GUIDELINES
The crystal oscillator of the Si4020 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 (C
0
) 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 C
0
and ESR values guarantee faster oscillator startup.
The crystal frequency is used as the reference of the PLL, which generates the RF carrier frequency (f
c
). Therefore, f
c
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 carrier frequency error.
Maximum XTAL Tolerances Including Temperature and Aging [ppm]
Bit Rate: 2.4kbps
30
60
90
120
150
180
210
315 MHz
30
75
100
100
100
100
100
433 MHz
20
50
75
100
100
100
100
868 MHz
10
25
40
60
75
100
100
915 MHz
10
25
40
50
75
75
100
Bit Rate: 9.6kbps
30
60
90
120
150
180
210
315 MHz
25
70
100
100
100
100
100
433 MHz
15
50
75
100
100
100
100
868 MHz
8
25
40
60
75
75
100
915 MHz
8
25
40
50
70
75
100
Bit Rate: 38.3kbps
30
60
90
120
150
180
210
315 MHz
dont use
30
75
100
100
100
100
433 MHz
don't use
20
50
75
100
100
100
868 MHz
don't use
10
30
40
60
75
100
915 MHz
don't use
10
25
40
60
75
75
Transmitter Deviation [+/- kHz]
Transmitter Deviation [+/- kHz]
Transmitter Deviation [+/- kHz]
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 C
0
.
Note: There may be other requirements for the TX carrier accuracy with regards to the requirements as defined by standards and/or channel
separations.
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相关代理商/技术参数
SI4020-I1-FTR
功能描述:射频发射器 Transmitter EZRadio RoHS:否 制造商:Micrel 类型:ASK Transmitter 封装 / 箱体:SOT-23-6 工作频率:300 MHz to 450 MHz 封装:Reel
SI-40219
制造商:BEL 制造商全称:Bel Fuse Inc. 功能描述:SI-40219
Si4021-A1-FT
功能描述:射频发射器 Transmitters IA4221 RoHS:否 制造商:Micrel 类型:ASK Transmitter 封装 / 箱体:SOT-23-6 工作频率:300 MHz to 450 MHz 封装:Reel
SI4021-A1-FTR
功能描述:射频发射器 Transmitter EZRadio RoHS:否 制造商:Micrel 类型:ASK Transmitter 封装 / 箱体:SOT-23-6 工作频率:300 MHz to 450 MHz 封装:Reel
SI-40222
制造商:BEL 制造商全称:Bel Fuse Inc. 功能描述:SI-40222
SI-40223
制造商:BEL 制造商全称:Bel Fuse Inc. 功能描述:SI-40223
SI-40227
制造商:BEL 制造商全称:Bel Fuse Inc. 功能描述:SI-40227
SI-40228
制造商:Bel Fuse 功能描述:CONN RJ-45 RCP 32 POS 2.54MM SLDR RA TH 48TERM 4PORT - Trays